LJ 


THE 


MANUFACTURE  OF  IRON, 


IN  ALL  ITS  VARIOUS  BRANCHES. 


INCLUDING 

A  DESCRIPTION  OF  WOOD-CUTTING,  COAL-DIGGING,  AND  THE  BURNING  OF  CHARCOAL 

AND  COKE  ;  THE  DIGGING  AND  ROASTING  OF  IRON  ORE  ;  THE  BUILDING  AND 

MANAGEMENT  OF  BLAST  FURNACES,  WORKING  BY  CHARCOAL,  COKE,  OR 

ANTHRACITE;  THE  REFINING  OF  IRON,  AND  THE  CONVERSION 

OF  THE  CRUDE  INTO  WROUGHT  IRON  BY  CHARCOAL 

FORGES  AND  PUDDLING  FURNACES. 

ALSO, 

A  DESCRIPTION  OP  FORGE  HAMMERS,  ROLLING  MILLS,  BLAST  MACHINES, 
HOT  BLAST,  ETC.  ETC. 

TO  WHICH  IS  ADDED, 

AN  ESSAY  ON  THE  MANUFACTURE  OF  STEEL. 


BY  FREDERICK  OVERMAN, 


MINING   ENGINEER. 


Pboenixville  Iron  Works. 

WITH   ONE   HUNDRED   AND   FIFTY   WOOD   ENGRAVINGS. 

(Kbition. 


PHILADELPHIA: 
HENRY  C.  BAIRD,  SUCCESSOR  TO  E.  L.  CAREY, 

S.  E.  CORNER  MARKET  AND  FIFTH  STREETS. 

1851. 


Entered  according  to  the  Act  of  Congress,  in  the  year  1849,  by 

HENRY  C.  BAIRD, 
in  the  Clerk's  Office  of  the  District  Court  for  the  Eastern  District  of  Pennsylvania. 


\ 


PHILADELPHIA  t 
T.  K.  AND  P.  G.  COLLINS,  PRINTERS. 


PREFACE. 


THIS  book  has  been  written  with  a  special  regard  to 
practical  utility.  In  what  manner  this  object  has  been 
fulfilled,  we  leave  the  intelligent  reader  to  judge.  The 
character  of  the  work  is  purely  technological.  This 
object  we  not  only  deemed  desirable  in  itself,  but  we 
were  necessarily  restricted  to  it  on  account  of  space. 
A  mere  description  of  materials  and  of  manipulations 
amounts  to  nothing  more  than  an  enumeration  and  re- 
cord of  facts.  This  we  considered  insufficient  to  satisfy 
the  wants  of  an  inquisitive  community.  Therefore,  each 
division  of  the  book  contains  a  philosophical  investigation 
concerning  the  apparatus  and  manipulations  applicable  to 
specific  cases,  as  well  as  the  basis  whence  their  relative 
advantages  are  deduced.  No  book  which  embodies  only 
a  collection  of  confused  or  partially  developed  facts  is 
adapted  either  to  attract  or  to  fix  the  attention  of  a 
thoughtful  mind.  The  little  interest  which  men,  even 
of  education  and  intelligence,  take  in  certain  mechanical 
pursuits  that  are  worthy  of  all  notice,  is  probably  to  be 
attributed  to  the  rarity  of  the  treatises  which  elucidate 
the  principles  such  pursuits  involve. — This  evil  we  have 
sought  to  avoid,  without,  at  the  same  time,  making  our 
book  so  scientific  as  to  render  it  useless  as  a  practical 
treatise. 

This  work  contains  imperfections  for  which  we  cannot 
consistently  ask  the  indulgence  of  the  reader.  It  may 
even  embody  errors;  these,  on  the  ground  of  human 

M18G173 


iy  PREFACE. 

frailty,  may  be  deemed,  by  the  kind-hearted  reader, 
excusable.  The  expression  of  one  fact  will,  we  hope, 
disarm  critics.  "We  make  no  claims  as  a  writer.  We 
make  this  statement,  not  only  because  the  language  of 
the  book  is  not  our  native  tongue,  but  because,  though  it 
were,  we  doubt  whether  we  should  be  able  to  exhibit  a 
reasonable  proficiency  in  its  use. 

Many  of  the  repetitions  which  the  reader  will  observe 
may  appear  to  be  superfluous.  Some  of  these  were  de- 
signed; others,  despite  every  precaution,  were  unavoid- 
able. In  verbal  communications,  we  are  enabled  to  draw 
attention  to  a  given  subject  by  a  bold  assertion,  or  a 
striking  illustration.  But  in  a  technical  work,  designed 
to  convey  important  information,  a  certain  amount  of 
repetition  is  almost  indispensable. 

Quotations  and  references  we  consider  inappropriate  in 
a  work  like  the  present.  But  we  have  not  hesitated  to 
insert  them,  where  this  could  be  done  without  interfering 
with  the  current  of  the  text.  In  addition  to  the  authors 
we  have  quoted,  we  acknowledge  our  indebtedness  to  the 
German  authors  Karsten,  Knapp,  and  Sheerer. 

The  publisher  has  spared  no  expense  in  relation  to  the 
typography  and  engravings  of  this  work,  which  have 
been  executed  in  a  manner  equal  to  anything  the  country 
can  afford.  Woodcuts  are  preferable  to  lithographic  or 
copperplate  illustrations,  on  account  of  the  facility  with 
which  they  can  be  printed  on  the  exact  spot  to  which 
they  belong.  If  the  book,  with  all  its  incongruities,  shall 
be  accepted  kindly  by  the  public,  our  labors  will  have 
been  more  than  compensated. 

F.  OVERMAN. 

PHILADELPHIA,  November,  1849. 


TABLE   OF   CONTENTS. 


CHAPTER  I. 

IRON  ORE. 

PAGE 

I.  Native  iron            .            .            .  .  .  .  .17 

II.  Oxide  of  iron        .            ...  .  .  .  .17 

a.  Protoxide  of  iron     .            .  .  .  .  .18 

6.  Magnetic  black  oxide  of  iron  .  .  .  .18 

c.  Peroxide  of  iron      .            .  .  .  .  .19 

d.  Hydrated  oxide  of  iron       .  .  .  .  .21 

III.  Carburets  of  iron             .            .  .  .  .  .23 

IV.  Sulphurets  of  iron            .            .  .  .  .  .24 

a.  White  sulphuret      .            .  .  .  .  .24 

b.  Yellow  sulphuret     .            .  .  .  .  .24 

V.  Phosphurets  of  iron         .            .  .  .  .  .25 

VI.  Arseniurets  of  iron           .            .  .  .  .  .25 

VII.  Chlorides  of  iron              .            .  .  .  .  .26 

VIII.  Sulphates  of  iron              .            .  .  .  .  .26 

IX.  Phosphate  of  iron             .            .  .  .  .  .27 

X.  Carbonate  of  iron              .            .  .  .  .  .28 

a.  Sparry  carbonate    .            .  .  .  .  .28' 

6.  Compact  carbonate             .  .  .  .  .29 

XI.  Titanate  of  iron    .......      30 

XII.  Chromate  of  iron              .            .  .  .  Jjj  .       31 

XIII.  Franklinite            .            .            .  •.  .  .  .31 

XIV.  General  remarks  .            .            .  .  .  .  .31 

a.  Theory  of  reducing  ore  to  metals  .  .  .  .32 

6.  Metals  and  oxygen              .  .  .  .  .32 

c.  Hydrates      .......      33 

d.  Reduction  of  oxides            .  .  .  .  .34 

e.  Reviving  of  metals              .  .  .  .  .34 

f.  Metals  and  sulphur             .  .  .  .  .36 

g.  Metals  and  phosphorus       .  .  .  .  .37 
7i.  Metals  and  carbon              .  .  .  .  .38 
t.  Metals  and  acids     .  .  38 


yi  CONTENTS. 

PAGE 

XV.  Roasting  of  iron  ore                      .            .            .  .  .39 

a.  Magnetic  oxide  of  iron        .            .            .  .  .39 

b.  Hydrated  oxide       .            .                         .  .  .39 

c.  Carburets  of  iron    .            .            .            .  .  .39 

d.  Sulphurets  ......      40 

e.  Phosphurets             .            .            .            .  .  .40 

f.  Arseniurets              .            .            .            .  .  .40 

g.  Chlorides     .            .            .            .            .  .  .40 

7i.  Sulphates    .......      40 

t.  Phosphates              .            .            .            .  .  .40 

k.  Carbonates               .            .            .            .  .  .40 

aa.  Roasting  in  ovens,  kilns     .            .            .  .  .41 

bb.  Roasting  in  mounds            .            .            .  .  .43 

cc.  Roasting  in  the  open  air,  in  heaps            .  .  .44 

XVI.  Cleaning  of  roasted  ore                .            .            .  .  .46 

XVII.  Theory  of  roasting  ore     .            .            .            .  .  .47 

XVIII.  Mixing  of  ore       .            .            .            ...  .  .48 

XIX.  Practical  remarks             .            .            .            .  .  .49 

a.  Magnetic  oxide  of  iron       .            .            .  .  .50 

6.  Sparry  carbonate    .            .            .            .  .  .50 

c.  Specular  iron  ore    .            .            .            .  .  .50 

d.  Hydrated  oxide  of  iron      .            .            .  .  .51 

e.  Compact  carbonate             .            .            .  .  .52 

XX.  Mining  of  iron  ore           .            .            .            .  .  .52 

XXI.  Fluxes       ........      68 

a.  Lime  .......      68 

b.  Magnesia     .            .            .            .            .  .  .71 

c.  Clay             .            .            .            .            .  .  .71 

d.  Silex            .            .            .            .            .  .  .71 

e.  Ashes  of  the  fuel    .            .            .            .  .  .72 

XXII.  Assay  of  iron  ore             ...*'.  72 


CHAPTER  II. 

FUEL. 

I.  Wood 80 

a.  Amount  of  water  in  wood              .            .            .  .80 

b.  Hard  and  soft  wood            .            .            .            .  ..81 

c.  Specific  gravity       .            .            .            .            .  .81 

d.  Ashes          .            .            .            .            .            .  .81 

e.  Practical  remarks   .            .            .            .            .  .83 

II.  Turf  or  peat          ......  85 

a.  Ashes          ......  86 

b.  Chemical  analysis  of  turf               .            .            .  .86 

c.  Practical  remarks               ....  37 


CONTENTS.  yii 

PAGE 

III.  Fossil  coal  .......      87 

a.  Brown  coal              .            .  .  .  .  .88 

b.  Water  in  brown  coal           .  .  .  .  .88 

c.  Ashes          .......      88 

d.  Chemical  composition         .  .  .  .  .89 

e.  Bituminous  coal      .            .  .  .  .  .89 

f.  Water  in  bituminous  coal  .  .  .  .90 

g.  Ashes          .            .            .  .  .  .  .90 

Chemical  composition         .  .  .  .  .91 

Ji.  Practical  remarks                .            .            .  .  .91 

i.  Classification           .            .            .            .  .  .91 

k.  Mining         .            .            .            .            .  .  .92 

1.  Anthracite  .            ...            .            .  .99 

Water          .......      99 

Ashes           .            .            .            .            .  .  .99 

Chemical  composition         .            .            .  .  .99 

Practical  remarks    .            .            .            .  fc  .99 

m.  General  remarks  on  fuel     .            .            .  .  .     100 

n.  Quantity  of  coal  in  different  parts  of  the  world  .  .     100 

IV.  Distillation  of  fuel  .  .  .  .  .  .102 

V.  Charring  of  wood  .  .  .  .  .  .103 

a.  Charring  in  pits      ......  103 

6.  Charring  in  heaps                .....  104 

c.  Charring  in  mounds            .....  108 

d.  Charring  in  ovens                .....  110 

e.  Brown  charcoal      ......  113 

f.  Distillation  in  closed  vessels           ....  114 

g.  General  remarks  on  charring         ....  114 

Ti.  Yield 115 

i.  Products  of  distillation       .....  117 

k.  Season  for  charring             .....  117 

VI.  Charring  of  turf  .  .  .  .  .  .117 

VII.  Charring  of  brown  coal  .  .  .  .  .119 

VIII.  Charring  of  bituminous  coal        .    •  .  .  .     119 

a.  Coking  in  heaps      ......     119 

6.  Coking  in  rows        .  .  .  .  .  .     121 

c.  Coking  in  ovens      ......     122 

d.  Coking  in  iron  retorts         .....     129 

IX.  General  remarks  on  coking  .....     129 

X.  Heat  liberated  by  fuel     .  .            .            .            .    132 

a.  Quantity  of  heat     .  .            .            .            .            .132 

6.  Quality        .            .  .            .            .            .            .136 

XI.  Analysis  of  fuel 137 


viii  CONTENTS. 

CHAPTER  III. 

REVIVING  OF  IRON. 

PAGE 

I.  Reviving  of  iron  in  a  crucible      .....  141 

II.  Reviving  of  iron  in  a  stuck,  or  wulf 's  oven        .  .  .  141 

III.  Reviving  of  iron  in  a  blue,  or  cast  oven  .  .  .  143 

IV.  Reviving  of  iron  in  various  blast  furnaces          .  .  .  144 

a.  Blast  furnace  in  the  Hartz  Mountains,  Germany  .  144 

6.  Blast  furnace  at  Malapane,  Silesia             .            .  .  145 

c.  Blast  furnace  for  smelting  bog  ore             .            .  .  146 

d.  Blast  furnace  for  smelting  spathic  ore,  Styria       .  .  147 

e.  Blast  furnace  in  Sweden     .....  148 

f.  Blast  furnace  in  Saynerhutte,  Germany    .            .  .  148 

g.  Blast  furnace  at  Cold  Spring,  N.  Y.                        .  .  150 
h.  Blast  furnace  in  Pennsylvania       .            .            .  .151 

V.  Modern  charcoal  blast  furnace    .  .  .  .  .151 

a.  Building  of  a  stack — cupola  blast  furnace  .  .     153 

6.  Starting  of  a  charcoal  furnace        ....     164 

c.  Charges  of  a  charcoal  furnace        ....     165 

d.  Practical  remarks   ......     166 

VI.  Coke  furnaces       .  .  .  .  .  .  .174 

VII.  Coke  furnaces  in  Hyanges,  France          ....     177 

VIII.  Anthracite  furnaces          ......     179 

IX.  Management  of  blast  furnaces     .....     183 

a.  In-wall,  or  lining    ......     183 

b.  Hearth         .  .  .  .  .  .  .183 

c.  Application  of  fire  .....     184 

d.  Charging  with  ore  .....     185 

e.  Nature  of  charges  .  .  .  .  .    185. 

/.  Tap-hole      .  185 

g.  Tuyeres       .  .  .  .  .  .185 

Ti.  Application  of  blast  .....     186 

i.  Height  of  damstone  .....     186 

k.  Slag 186 

L  Tools  .  .  .  .  .  .  .187 

m.  Management  of  the  tuyere              .            .            .            .  187 

n.  Management  of  the  timp    .....  188 

o.  Accumulation  of  cold  clinkers  in  the  hearth         .            .  190 

p.  Tapping  of  iron      ......  190 

q.  Causes  of  disorder               .....  190 

r.  Wet  bottom  stone                .....  191 

s.  Filling  of  the  furnace         .  .  .  .  .191 

t.  Coal  charges            .            .            .            .            ...  194 

u.  Size  of  coal             ......  195 

v.  Ore  charges             ......  195 

w.  Size  of  ore               ......  196 

x.  Mixing  of  ores        ......  197 


CONTENTS.  ix 

PAGE 

y.  Number  of  charges             .                        ...  200 

z.  Number  of  tuyeres  require.d  in  a  furnace  .  .  200 

aa.  Time  of  tapping  iron  .....  201 

bb.  Quality  of  iron  depending  on  the  tuyere  .  .  201 

cc.  Quality  of  iron  depending  on  burden  .  .  .  202 

dd.  Quality  of  iron  depending  on  flux  .  .  .  203 

ee.  Quality  shown  by  cinder  .....  203 

//.  Scaffolding  in  the  furnace  .  .  .  204 

gg.  Flame  of  trunnel-head  ...  .  204 

hh.  Appearance  of  melted  iron             ....  205 

Theory  of  the  blast  furnace         .  .  .  .  .206 

a.  Combustion              ......  206 

b.  Nature  of  combustion  in  a  blast  furnace               .            .  207 

c.  Composition  of  gases          .....  207 

d.  Reduction  of  ore     .                                     .                         .  209 

e.  Operation  in  the  furnace    .  .  .  .211 

f.  Conditions  required  in  the  interior  .  .  .211 

g.  Theory  deduced  from  practice        ....  212 
^.  Conditions  of  the  ore  in  the  furnace          .            .            .  214 
i.  Composition  of  ore  best  adapted  to  receive  and  retain 

carbon               ......  214 

k.  Influence  of  foreign  matter  contained  in  the  ore               .  215 
I.  Influence  of  foreign  matter  relative  to  absorption  of  car- 
bon                    .            .216 

m.  Clay,  silex,  and  lime           .....  217 

n.  Clay,  silex,  and  lime  in  ore             ....  217 

o.  Magnetic  ore — want  of  cinder        ....  218 

p.  Causes  of  white  iron           .....  218 

q.  Difficulty  of  smelting  gray  iron  from  clay  and  silicious 

ores       .......  219 

r.  Ores  which  flux  themselves             ....  220 

s.  Calcareous  ore         ......  221 

t.  Clay  ores     .......  222 

u.  Capacity  of  matter  for  carbon        ....  222 

v.  Amount  of  fuel  consumed  by  different  ores          .            .  223 
w.  Fusibility  of  ores    .            .            .            .            .            .225 

x.  Effects  of  fusibility  .  .  .  .  .225 

y.  Degree  of  fusibility  of  ore  compositions    .            .            .  226 

z.  Effect  of  the  alkalies  in  cinder       ....  228 

aa.  Fusibility  of  iron  and  cinder          ....  229 

bb.  Nature  of  fluxes      ......  230 

cc.  Composition  of  cinder         .            .            .            .            .  231 

dd.  Titanium  in  cinder             .            .            .            .            .  235 

ee.  Method  of  working  titaneous  ore               ...  236 

ff.  Cinder  from  steel  iron        .....  236 

gg.  Construction  of  furnace  for  making  steel  metal    .            .  238 

hh.  Cinder  from  a  coke  furnace                        .            .            .  239 


CONTENTS. 
CHAPTER  IV. 

MANUFACTURE' OF  WROUGHT  IRON. 

PAGE 

I.  Oriental  mode  of  making  iron     .....    243 
II.  Catalan  forge        ...  .245 

a.  Quality  of  iron  from  the  Catalan  forge      .  .  .    248 

b.  Stuck  oven 248 

III.  German  forge 249 

a.  Material  employed  in  the  German  forge    .  .  .251 

b.  Form  of  hearth       ....  .251 

c.  Influence  of  the  quality  of  coal     .  .  ,  .251 

d.  Use  of  fluxes 252 

e.  Size  and  form  of  the  hearth  ....     252 

/.  Manipulation  ......    253 

g.  Tools  .  .  .  .      •      .  .  .255 

h.  Yield 255 

IV.  Finery  fire  ....  .    256 

a.  Quality  of  the  refined  iron  ....    259 

V.  Puddling  furnaces  .  .  .  .  .  .259 

a.  Construction  of  furnaces    .....    260 

b.  Exterior 262 

c.  Puddling  and  boiling         .....    265 

d.  Manipulation          ......    265 

e.  Tools 266 

/.  Puddling 267 

g.  Boiling        .  .  .  .  .  .  .268 

Ti.  Difference  in  the  construction  of  puddling  and  boiling 

furnaces  .  .  .  .  .  .270 

i.  Cinder  from  puddling  and  boiling  .  .  .    270 

k.  Anthracite  furnace  .  .  .  .  .271 

Z.  Heating  stove          ......    274 

m.  Puddling  at  Hyanges,  France        ....    274 

n.  Improvement  of  puddling  by  addition  of  fluxes  .  .276 

o.  Practical  application  of  fluxes       ....    278 

VI.  General  remarks  on  charcoal  forges        ....    280 

a.  Location  of  a  forge  ' .  .  .  .  .    280 

b.  Ores  adapted  to  the  charcoal  forge  .  .  .    281 

c.  Quality  of  metal  required  ....    281 

d.  Site  of  the  forge      .  .  .  .  .  .281 

VII.  General  remarks  on  puddling      .....  282 

a.  Quality  of  iron        .  .  .  .  .  .282 

b.  Boiling  process       ......  283 

c.  Iron  boshes,  and  brick  or  soapstone  lining           .            .  283 

d.  Effect  of  iron  boshes  on  the  iron  manufactured  .            .  285 

e.  Cold  iron  boshes     ......  288 

/.  Iron  for  specific  purposes  .....  288 


CONTENTS.  xi 

PAGE 

g.  Elements  of  pig  iron,  and  their  effect  on  the  iron  manu- 
factured ......    291 

"h.  Mixing  of  pig  iron  and  artificial  fluxes    .  .  .    294 

z.  Hearth  of  a  furnace  .....     298 

k.  Roof  of  a  furnace  .....    299 

1.  Depth  of  the  bottom  .  .  .  .  .299 

m.  Dimensions  of  the  grate     .....    300 

n.  Fuel  .  .  .  .  .  .  .300 

0.  Heating  stoves        ......    301 

p.  Wages         .  .  .  .  .  .  .301 

q.  Yield 301 

VIII.  General  remarks  on  refining       .....    302 
a.  Various  methods  of  refining          ....    304 

IX.  Theory  of  refining  and  puddling  ....    305 

a.  Difference  between  cast  and  wrought  iron  .  .    305 

b.  Impurities  contained  in  wrought  iron       .  .  .     307 

c.  Causes  of  cold-short  iron    .....    309 

d.  Removal  of  impurities        .  .  .  .  .310 

e.  Nature  of  the  combination  of  iron  and  other  matter        .    311 

f.  Iron  containing  calcium  and  silicon          .  .  .     312 

g.  Cause  of  inferior  pig  iron  .  .  .  .314 
h.  Cinder,  the  criterion  of  the  quality  of  iron          .  .316 

1.  Influence  of  cinder  on  the  permanency  of  the  fibre  in 

wrought  iron     ......  318 

k.  Fusibility  of  iron  and  cinder;  composition  of  cinder      .  320 

I.  Critical  view  of  the  present  mode  of  refining       .  .  330 

m.  Philosophy  of  improving  iron        ....  332 

n.  Qualities  of  wrought  iron  ....  333 

CHAPTER  V. 

FORGING  AND  ROLLING. 

I.  Forge  hammers     .......    334 

a.  Tilt  hammer  .  .  .  .  .  .    334 

6.  T  hammer   .  .  .  .  .  .  .337 

c.  Brest  hammer         ......     338 

d.  Improved  jack         .  .  .  .  .  .    338 

e.  Steam  hammer        ......    339 

/.  Shingling  rods        .  .  .  .  .  .339 

g.  Faces  of  hammers  and  anvils         ...  .  .    340 

II.  Squeezers  .......    341 

a.  Lever  squeezer        ......    341 

6.  Rotary  squeezer      ......    342 

III.  Roughing  rollers  ......    344 

a.  Form  of  the  grooves  .....    346 

6.  Flat  bar  rollers  347 


xii  CONTENTS. 

PAGE 

c.  Construction  of  housings  and  rollers         .  .  .     349 

d.  Coupling-box,  cam-box,  and  junction-shafts          .  .     352 

e.  Flywheel     .  .  .  .  .  .  .353 

IV.  Merchant  mill       .  .  .  .  .  ...     354 

a.  Small  rod  iron         ......     354 

5.  Eound  and  square  iron       .....     356 

c.  Hard  rollers  ......     356 

d.  Adjusting  rollers     .  .  .  .  .  .357 

e.  Flat  rollers  for  small  rods  ....     357 

f.  Wire  and  hoop  rollers         .  .  .  .  .358 

V.  Heavy  bar  and  railroad  iron  rollers         .  .  .  .358 

a.  Form  of  rails          ......     359 

6.  Rollers  for  rails       .  .  .  .  .  .360 

c.  Shingling  of  rail  piles ;  cutting  off  the  fagot  ends  .    362 

VI.  Sheet  iron  .  .  .  .  .  .  .365 

a.  Necessity  of  re-heating  blooms      ....  366 

b.  Machinery  for  making  sheet  iron               .            .            .  366 

c.  Wrought  iron  standards  for  thin  sheet  iron          .            .  367 

d.  Boiler-plate             ......  368 

e.  Common  sheet  iron             ......  369 

f.  Color  of  sheet  iron             .....  371 

VII.  Re-heating  furnaces          .  .  .  .  .  371 

a.  Size  of  grate  .  .  .  .  .  372 

6.  Quantity  of  iron  re-heated     .        .  .  .  •          .  373 

c.  Scrap  furnaces        ......  374 

VIII.  Heating  ovens       .......  374 

a.  Fuel  in  heating  ovens         .....  375 

6.  Ancient  form  of  the  oven  ....  375 

c.  Modern  heating  oven          .  .  .  .  .  376 

IX.  Shears  and  turning  machines      .....     378 
a.  Turning  of  rollers  .....     378 

6.  Hand  shears  ......     378 

c.  Force  shears :  with  excentric,  and  with  crank      .  .    379 

d.  Fastening  the  cutters         .  .  .  .  .381 

X.  Tools 382 

XI.  General  remarks  ......    383 

a.  Catalan  fires  .  .  .  .  .  .383 

6.  Hammers  .....  383 

c.  Rolling  mills  ......     384 

d.  Small  rod  and  hoop  iron     .....    385 

e.  Wire  iron  ......    385 

/.  Railroad,  bar,  and  heavy  iron        .  .  .  .386 

g.  Piling  of  iron         ......    387 

h.  Sheet  iron  ......     389 

t.  Nails  .  391 


CONTENTS.  xiii 

CHAPTER  VI. 

BLAST  MACHINES. 

PAGE 

I.  Wooden  bellows  of  the  common  form     ....     394 
II.  Wooden  cylinder  bellows  .  .  .  .  .395 

a.  Double  stroke  tubs  .....    396 

b.  Construction  of  tubs  .....     397 

III.  Iron  cylinder  blast  machines       .....    398 

a.  Double  cylinders,  with  beams        ....    398 

b.  Horizontal  cylinder  .....     399 

c.  Moving  power  for  blast  machines  .  .  .     400 

IV.  General  remarks  on  blast  machines         ....    400 

a.  Size  of  blast  cylinder          .....  401 

b.  Size  and  form  of  valves       ......  401 

c.  Advantages  of  vertical  cylinder     ....  403 

d.  Packing  of  the  piston         .  .  .  .  .  403 

V.  Various  forms  of  blast  machines  ....     404 

a.  Trompe        .  .  .  .  .  .  .405 

b.  Chain-trompe  ......    405 

c.  Gasometer  bellows  .....     405 

d.  Screw  blast  machine  .....    406 

VI.  Fan  blast  machines          ......    407 

a.  Improved  fan          ......    409 

c.  Pressure  in  a  fan    ......    409 

VII.  Receivers,  or  regulators  of  blast  ....    410 

a.  Dry  receiver  .  .  .  .  .  .411 

VIII.  Blast  pipes 413 

a.  Nozzles        .......    415 

IX.  Tuyeres     .  .  .  .  .  .  .  .417 

a.  Tuyeres  for  forges  .  .  .  .  .     418 

b.  Water  tuyere  ......     419 

Number  of  tuyeres  .....    422 

X.  Valves       ........  423 

XI.  Manometer  .......  424 

XII.  General  remarks  on  blast  machines         ....  426 

a.  Effect  of  blast  machines     .....  426 

b.  Location  of  blast  machines  ....  426 

CHAPTER  VII. 

HOT  BLAST. 

I.  Hot  air  apparatus  ......    428 

a.  With  round  pipes    ......    429 

b.  With  straight  pipes  .  .  .  .  .431 


CONTENTS. 

PAGE 

c.  Cleaning  of  the  tuyere        .  .  .  .  '          .    432 

d.  Measurement  of  temperature         ....     433 

II.  Theory  of  hot  blast          .  .  .  .  .  .434 

a.  Chemical  effect        ......    434 

5.  Chemical  effect  in  reducing  ore      ....    436 

c.  Effect  on  cinder       ......    437 

d.  Effect  on  iron          ......    437 

III.  General  remarks  on  hot  blast      .....    440 
CHAPTER  VIII. 

WASTE  HEAT  AND  GAS. 

I.  Waste  heat           .           .           .  .  .  .  .444 

a.  Of  mill  furnaces     .            .  .  .  .  .444 

6.  Of  blast  furnaces     .            .  .  .  .  .445 

c.  Advantages  of  waste  heat '  446 

II.  Gas  .  .  .  .  .  .  .  .446 

a.  Carbonic  oxide  gas  .....    446 

b.  From  the  blast  furnace        .....    447 

CHAPTER  IX. 

FIRE  BRICK  AND  REFRACTORY  STONES. 

I.  Native  refractory  stones  .  .  .  .  .453 

a.  Sandstone   .......    453 

6.  Clay  slate    .  .  .  .  .  .  .453 

c.  Talc  slate    .  .  .  .  .  .  .454 

II.  Artificial  refractory  stones  .  .  .'  .  .  454 

a.  Fire  brick    .......  454 

&.  Artificial  sandstone  .....  456 

c.  Refractory  mortar  .  .  .  .  .  457 

III.  Conductors  of  heat  ......    458 

CHAPTER  X. 

MOTIVE  POWER. 


CHAPTER  XI. 

MANUFACTURE  OF  STEEL. 

I.  Damascus  steel     .......  465 

II.  German  steel        .......  466 

a.  From  ore     .            .            .            .            .            .            .  466 

6.  Woots          .......  466 

c.  From  crude  plate  iron        .....  466 

d.  Steel  on  wire  drawplates    .  .  .  .  .468 


CONTENTS.  XV 

PAGE 

III.  Iron  for  blistered  steel     .  .  .  .  .  .469 

a.  Ore  for  making  the  iron     .....     469 

b.  Iron  for  making  blistered  steel       ....    470 

IV.  Blistered  steel      .  .  .  .  .  .  .471 

a.  Quality  of  the  steel  .....    474 

6.  Influence  of  the  hammer  on  blistered  steel  .  .    475 

V.  Cast  steel  .  .  .  .  .  .  .475 

VI.  General  remarks  on  steel  .....    478 

Chemical  composition  of  steel       ....    481 

Hardening  of  steel  .  .  .  .  .483 

CONCLUSION  ,    484 


APPENDIX. 

Table       I.  Composition  of  crude  cast  iron         ....    486 

Table      II.  Composition  of  gray  cast  iron  ....     487 

Table    III.  Composition  of  steel  metal    .....    487 

Table    IV.  Composition  of  forge  crude  iron       ....    488 

Table      V.  Composition  of  wrought  iron  ....    488 

Table    VI.  Decomposition  and  recomposition  of  materials  in  the  blast 

furnace      .......    489 

Table  VII.  Specific  gravity  of  matter     .....    489 

Table  VIII.  Degrees  of  heat  generated  by  perfect  combustion  .  .    490 

Table     IX.  Degrees  of  heat  at  which  substances  melt  .  .  .    490 

Table      X.  Capacity  of  matter  for  latent  heat  .  .  .    490 

Table     XI.  Expansion  of  air  by  heat      .....    491 

Table  XII.  "Weight  of  substances  .  .  .  .  .491 

Table  XIII.  Weight  of  a  superficial  foot  of  sheet  iron    .  .  .491 

Table  XIV.  Weight  of  rod  iron  one  foot  in  length         .  .  .492 


ON   THE 

MANUFACTURE   OF   IRON. 

CHAPTER    I. 

IRON  ORE. 

A  GEOLOGICAL  classification  of  the  ores  of  iron  is,  in  our  case,  not 
the  proper  way  to  divide  the  subject  before  us  :  it  would  not  include 
that  clear,  comprehensive,  practical  demonstration  needed  for  our 
purpose;  and  we  choose,  therefore,  a  division  based  upon  the  compo- 
sition of  the  material,  or  a  Chemical  classification.  According  to 
this,  we  shall  divide  the  iron  ores  proper  into  Native  Iron;  Oxides, 
Carburets,  Sulphurets,  Arseniurets,  and  Phosphurets  of  Iron;  Chlo- 
rides, Sulphates,  Phosphates,  Carbonates,  and  Titanates  of  Iron. 

I.  Native  Iron. 

The  deposits  of  native  iron  are  very  limited,  and  the  insufficient 
quantity  of  material  it  affords,  precludes  it  from  being  ranged,  for 
our  purpose,  among  the  iron  ores.  We  notice  it  as  a  matter  of 
curiosity,  merely  to  complete  the  class.  Native  iron  has  been  found 
in  Canaan,  Conn.,  in  a  vein  or  plate  two  inches  thick;  it  is  suffi- 
ciently ductile  to  be  wrought  into  nails  by  a  blacksmith.  It  was 
found  in  a  mica  slate  rock,  upon  a  primitive  mountain,  and  very 
much  intermixed  with  plumbago.  In  France  and  Germany  native 
iron  has  also  been  found ;  but  there  are  serious  doubts  whether  it 
is  formed  by  nature ;  and  its  existence  may  probably  be  assigned 
to  the  previous  burnings  of  stone  coal  in  its  vicinity. 

II.   Oxides  of  Iron. 

These  constitute  the  most  important  class  for  the  manufacture  of 
iron.     They  may  be  considered  under  four  distinct  subdivisions, 
namely,  Protoxide,  Magnetic  Oxide,  Peroxide,  and  Hydrated  Oxide 
of  Iron. 
2 


18  MANUFACTURE   OF  IRON. 

a.  Protoxide  of  Iron  has  never  been  found  as  a  natural  deposit, 
and  it  is  difficult,  even  in  the  chemical  laboratory,  to  make  it.     It 
can  be  made  by  precipitating  salts  of  the  protoxide  by  caustic 
soda ;  but  it  is  very  apt  to  oxidize  in  being  washed  and  strained, 
whereby  a  part  of  it  is  converted  into  oxide.     The  best  way  to 
produce  it,  is  to  oxidize  iron  heated  to  redness  by  means  of  steam. 
It  is  of  a  black  color,  attracted  by  the  magnet,  and  very  hard. 
It  is  composed  of 

77c23  iron 
22.77  oxygen 

100.00  peroxide  of  iron. 

Should,  therefore,  an  iron  ore  exist  of  this  composition,  it  could 
not  contain  more  than  77  parts  of  iron  in  100  parts  of  ore. 

b.  The  next  degree  of  the  oxidation  of  iron  is  the  Magnetic  Black 
Oxide  of  Iron,  Loadstone.     Its  color  is  a  grayish-black  ;  and  when 
rubbed,  it  gives  a  black  powder.     It  is  strongly  attracted  by  the 
magnet,  and  is  magnetic  itself.    It  is  altered  neither  by  nitric  acid 
nor  the  blowpipe.     It  dissolves  slowly  in  hydrochloric  and  diluted 
sulphuric  acids,  the  former  of  which  dissolves  the  protoxide,  and 
leaves  a  red  powder,  peroxide,  undissolved.     This  circumstance 
is  evidence  of  its  being  no  particular  oxide  of  iron,  but  a  mixture 
of  the  protoxide  and  the  peroxide.    Its  composition  is,  in  100  parts, 

71.79  iron 
28.21  oxygen 

100.00  magnetic  oxide  of  iron  ; 

or,  it  consists  of  31  parts  of  the  protoxide  and  69  parts  of  the 
peroxide  of  iron ;  and  in  100  parts  of  ore  there  cannot  be  more 
than  71  per  cent,  of  iron. 

This  species  of  iron  ore  constitutes  a  large  body  of  the  native 
deposits.  It  is  found  in  Sweden,  Norway,  Siberia,  China,  Siam, 
the  Philippine  Islands,  Germany,  France,  and  very  little  in  Eng- 
land. There  is  a  large  deposit  at  Lake  Champlain,  N.  Y.,  of  the 
best  quality.  It  is  also  found  in  Bridgewater,  Vt.,  Marlborough, 
Vt.,  and  Franconia,  N.  H.;  and  New  Jersey  and  the  State  of  New 
York  contain  it  in  large  quantities.  The  exploration  of  the  north- 
west of  the  United  States  promises  an  addition  to  the  already  known 
valuable  deposits,  for  the  iron  mountain  in  Missouri  appears  to 
belong  to  this  class.  This  is  one  of  the  most  valuable  ores,  fur- 
nishing, by  proper  treatment,  the  best  quality  of  iron.  From  it  the 
main  body  of  the  superior  iron  from  Sweden,  Russia,  and  Germany 


IRON   ORE.  19 

is  manufactured;  but  the  modern  improvements  in  manufacturing, 
particularly  the  hot  blast,  appear  to  impair  its  good  disposition,  and 
furnish  inferior  qualities  of  iron.  We  will,  in  the  following  chap- 
ters, explain  the  reasons  why  this  ore  requires  particular  treat- 
ment and  attention. 

Magnetic  iron  occurs  in  primitive  rocks,  commonly  in  gneiss, 
sometimes  in  clay  hornblende  or  chlorite  slate,  greenstone,  and 
limestone,  and  is  mixed  with  epidote,  pyroxene,  and  garnet.  We 
never  find  it  in  more  recent  geological  deposits.  Its  crystalline  form 
is  an  octahedron,  and  it  varies,  in  size  from  an  inch  to  the  finest 
sand.  It  is  seldom  found  in  solid  masses. 

c.  Oxide  of  Iron,  Peroxide  of  Iron,  Iron-glance,  Specular  Iron, 
and  Red  Iron  Ore. — These  subdivisions  of  the  oxides  form  a  very 
extensively  distributed  ore.  This  ore  is  very  hard,  sometimes  the 
color  of  polished  steel,  and  crystals  of  this  kind  transmit  light 
through  the  edges,  and  appear  to  be  beautifully  red.  When  coarse, 
the  oxide  is  of  a  brown  color ;  but  its  powder  is  always  red,  thus  dis- 
tinguishing it  from  the  magnetic  oxide.  It  is  infusible  before  the 
blowpipe,  but  melts  with  borax,  and  forms  a  green  or  yellow  glass. 
Heated  hydrochloric  acid  is  the  only  acid  able  to  dissolve  it.  By 
high  temperatures,  without  the  addition  of  any  other  matter,  it  is 
reduced  to  the  magnetic  ore.  The  magnet  does  not  attract  it,  nor 
is  the  magnet  attracted  by  the  iron. 

Oxide  of  iron  is  composed,  in  100  parts,  of 
69.34  iron 
30.66  oxygen 

100.00  protoxide  of  iron. 

This  oxide  of  iron  is  used  for  various  purposes  besides  the  manu- 
facture of  iron :  as  calcined  hydrate,  it  forms  a  red-brown  paint 
Spanish  or  Indian  brown,  which  is  the  most  durable  of  all  paints 
for  preserving  wood  and  iron.  In  northern  Europe  the  houses  of 
the  peasantry  are  mostly  painted  with  it.  It  serves  for  polishing 
silver  and  gold,  and  for  that  purpose  is  manufactured  from  cop- 
peras, which  is  calcined  along  with  common  salt.  The  red  color 
of  the  common  brick  is  oxide  of  iron. 

Those  varieties  of  specular  iron  ore  which  have  lost  their  metallic 
appearance,  are  called  red  iron  ore;  they  are  either  fibrous  or  solid, 
compact  or  ochry ;  sometimes  they  form  a  firmly  connected  mass  of 
a  red  impalpable  powder.  The  scaly  red  iron,  and  the  red  iron  foam 
belong  to  this  class ;  in  masses  they  are  but  slightly  coherent.  The 


20  MANUFACTURE   OF   IRON. 

whole  variety  is  in  close  connection  with  the  micaceous  specular 
iron,  between  which  and  the  crystallized  oxide  of  iron  is  an  unin- 
terrupted transition.  If  this  variety  of  ore  is  mixed  with  foreign 
matter,  its  red  color  is  sometimes  altered — and,  mixed  with  silica, 
lime,  &c.,  turns  into  hydrates  of  iron  ;  but  an  admixture  of  clay 
does  not  alter  its  red  color,  and  the  ore  is  called  clay  ore.  Reddle, 
jaspery  clay  ore,  columnar,  and  lenticular  iron  ore,  are  of  this  kind: 
the  first  of  which  is  compact,  friable ;  the  second  very  hard,  of 
conchoidal  fracture;  the  third,  distinguished  by  its  columnar  forms; 
and  the  latter,  by  its  granular  composition. 

This  variety  of  ore  yields  very  unequal  amounts  of  iron;  it  ranges 
from  the  red  clay  of  hardly  12  per  cent,  of  iron,  to  the  rich  micaceous 
ore,  which  is  pure  oxide  of  iron.  In  this  case,  the  evidence  of  sense 
is  no  safe  dependence,  for  a  very  poor  clay  appears  sometimes  as 
red  as  the  richest'ore — though  by  drying  the  specimens,  a  difference 
in  color  may  be  perceived:  still,  it  would  be  premature  to  infer  from 
this,  what  amount  of  iron  a  given  specimen  contains.  The  only 
way  to  ascertain  the  quantity  of  iron  is  by  chemical  analysis,  and 
the  humid  is  the  only  test  we  can  depend  upon.  But  this  variety 
of  ore  yields  always  good  and  strong  iron,  and  is,  perhaps,  on  that 
account,  the  most  valuable;  for  the  iron  manufactured  from  it  is  the 
most  tenacious  of  all  known  kinds.  It  improves,  even  in  small  quan- 
tities, all  inferior  ores,  and  forms  a  most  excellent  flux  in  the  blast 
furnace.  The  damask  iron  of  Persia  and  the  woots  of  India  are 
manufactured  from  specular  iron  ore.  Red  iron  ore  occurs  most 
commonly  in  ancient  rocks,  and  transition  clay  slate  is  generally  its 
locality,  where  the  best  and  richest  beds  are  deposited.  The  Island 
of  Elba  is  justly  celebrated  for  an  inexhaustible  abundance  of  specu- 
lar iron,  which  has  been  worked  since  immemorial  antiquity.  The 
total  height  of  the  metalliferous  mountain  is  more  than  600  feet,  and 
never  will  be  exhausted.  Specular  iron  ore  is  found  throughout 
Asia,  Corsica,  Germany,  France,  Sweden,  and  in  almost  every 
country.  The  United  States  of  America  have  yet  afforded  no  amount 
worth  noticing  of  the  better  qualities ;  but  immense  beds  of  infe- 
rior quality,  for  instance,  the  Pittsburgh  coal  field,  are  loaded  with 
some  very  valuable  red  clay  ores,  interspersed  with  nodules  of  the 
specular  kind.  Massachusetts,  Ohio,  and  the  western  part  of  New 
York,  contain  similar  deposits.  Specular  iron  ore  is  found  in  crys- 
tals in  the  craters  of  volcanoes,  the  result  of  the  evaporation  of  chlo- 
rides of  iron  in  the  fissures  of  lava.  It  forms  heavy  beds  in  transi- 
tion mountains,  and  is  frequently  found  imbedded  in  clay  in  the  shape 


IRON   ORE.  21 

of  nodules  of  irregular  masses.  It  is  common  in  beds  of  spathic 
iron,  in  Styria  and  Carinthia,  and  generally  associated  with  other 
ores  of  iron  or  earthy  minerals,  as  epidote,  hornblende,  augite,  cal- 
careous spar,  and  quartz. 

All  the  red  clays  belong  to  this  class,  and,  when  they  contain 
more  than  20  per  cent,  of  metal,  may  be  considered  an  ore  of  iron. 

d.  Hydrated  Oxide  of  Iron,  Brown  Oxide  of  Iron,  Brown  Iron 
Stone,  Hematite. — We  have  here  a  class  of  iron  ores  which,  in 
quantitative  importance,  supersede  any  other  kind  in  the  United 
States.  Hydrated  oxide  of  iron  always  affords  a  yellow  powder, 
without  any  shade  of  red,  sometimes  brownish,  or  even  velvet 
black.  At  the  blowpipe  it  turns  brown  or  red,  and>in  the  reducing 
flame  black,  and  melts  into  a  black  cinder.  Burnt  or  roasted,  it 
is  strongly  attracted  by  the  magnet,  but  not  in  its  raw  state.  Cal- 
cined, it  yields  a  red  powder,  oxide  of  iron,  and  is  employed  for 
the  same  purposes  as  the  oxide.  The  yellow  or  brown  varieties 
contain  a  large  admixture  of  water  in  chemical  combination,  and 
hence  they  are  called  hydrates. 

Hydrated  oxide  of  iron  consists,  in  100  parts,  of 
59.15  iron 
26.15  oxygen 
14.70  water 

100.00  hydrated  oxide  of  iron. 

Brown  or  yellow  iron  ore,  therefore,  never  contains  more  than 
59.15  Ibs.  of  iron  in  100  Ibs.  of  ore. 

The  mineralogical  term  of  this  ore  is  Limonite  ;  it  comprises  a 
great  number  of  compound  varieties.  Its  forms  are  various — glob- 
ular, reniform,  stalactitic,  and  raamillary.  It  presents  great  variety 
of  surface,  being  smooth,  granulated,  reniform,  drusy,  columnar ; 
and  it  is  often  an  impalpable  powder.  It  is  a  species  which,  on  ac- 
count of  differences  in  regard  to  mechanical  composition,  has  re- 
ceived a  great  diversity  of  names  ;  still,  all  the  varieties  are  of  the 
same  chemical  composition,  unless  adulterated  by  foreign  matter. 
The  whole  class  is  the  result  of  the  decomposition  of  other  iron  com- 
pounds, namely,  iron  pyrites,  carbonates,  red  oxides,  sulphates,  &c. 
The  fibrous  limonite,  or  brown  hematite,  contains  sometimes  beauti- 
ful crystals  of  the  hydrate,  and  is  known  under  the  name  of  pipe 
ore,  brown  ore,  and  shell  ore;  it  is  then  reniform,  and  consists  of 
alternate  layers  of  different  color,  or  coats  of  different  hardness.  To 
this  species  belong  also  a  great  variety  of  impalpable  and  scaly 
compounds. 


22  MANUFACTURE   OF   IRON. 

Limonite  occurs  in  beds  and  veins,  generally  accompanied  by 
spathic  iron,  calcareous  spar,  aragonite  or  quartz.  We  find  these 
beds,  or  veins,  both  in  ancient  and  secondary  rocks,  in  tertiary  de- 
posits, in  diluvium,  and  alluvium.  In  the  older  rocks,  limonite  is 
generally  derived  from  pyrites,  and  in  the  coal  measures  from  car- 
bonates ;  we  find  it  in  globular  masses  imbedded  in  clay,  in  sand- 
stone, and  in  bogs. 

Limonite  is  very  plentiful  all  over  the  globe,  particularly  in  the 
United  States ;  vast  beds  are  near  Salisbury  and  Kent,  in  Connec- 
ticut, resting  in  mica  slate ;  they  are  of  the  best  kind  of  brown 
hematite,  and  are  fibrous.  In  the  State  of  New  York,  near  Beek- 
man  and  Amenia,  are  similar  deposits.  Massachusetts  is  favored 
with  that  kind  of  ore ;  also  Vermont,  Maryland,  and  Ohio.  The 
whole  iron  business  of  Hanging  Rock  depends  upon  it.  Ken- 
tucky, Tennessee,  and  Alabama,  abound  in  inexhaustible  beds  of 
the  best  quality.  But  above  all,  Pennsylvania  has  the  richest  varie- 
ties of  this  kind.  No  doubt  there  is  more  in  the  United  States  than 
we  at  present  know  of,  and  the  great  valley  between  the  Rocky 
Mountains  and  the  Alleghanies  is  a  natural  basin  for  all  such  valu- 
able deposits  swept  down  from  Canada,  and  the  impenetrable  north. 

Limonite  is  the  main  source  of  the  iron  of  commerce  all  over 
the  globe.  It  affords  an  easy  and  cheap  material,  and  the  better 
varieties  are  excellent  iron  ;  but  we  have  to  be  careful  in  the  selec- 
tion of  the  ore  beds.  The  eastern  ore  is  generally  of  prime  qua- 
lity ;  so  is  that  of  Hanging  Rock  in  Ohio ;  that  of  Tennessee  and 
Alabama  is  of  as  good  a  quality  of  this  kind  as  one  could  desire ; 
but  the  deposits  of  the  coal  formation,  the  pipe  ores,  and  bog  ores, 
are  to  be  carefully  selected  in  reference  to  quality.  This  kind  of 
ore  in  the  older  rocks  is  generally  good,  but  where  it  is  derived 
from  more  recent  deposits,  it  contains  some  of  the  original  matter 
from  which  it  is  decomposed.  The  pipe  ore  is  decomposed  sul- 
phuret,  and  frequently  we  find  a  core  of  pyrites  in  the  centre ;  then 
the  ore  furnishes  hot-short  iron ;  but,  carefully  roasted,  the  sulphur 
of  the  pyrites  can  be  mostly  evaporated.  The  hydrates  of  the  coal 
formation  are  mainly  derived  from  spathic  iron,  and  frequently  con- 
tain carbonic  and  sulphuric  acids,  which  impair  the  quality  of  the 
metal,  but  can  be  removed  by  a  careful  roasting  of  the  ores.  Bog  ores, 
which  mostly  contain  phosphoric  acid,  are,  for  the  manufacture  of 
pig  metal,  incurable,  for  the  phosphorus  cannot  be  separated  by 
roasting;  but  this  separation  can  be  effected  in  the  forge,  and  hence, 
deserves  consideration.  In  the  main,  this  kind  of  ore  furnishes  an 


IRON    ORE.  23 

excellent  material  in  the  blast  furnace,  yields  cheap  pig  metal, 
and  of  all  classes  of  ore  is  the  most  available  for  improvement  in 
the  forge — as  well  in  the  charcoal  forge  as  in  the  puddling  furnace. 

III.   Carburets  of  Iron. 

Iron  has  a  great  affinity  for  carbon,  but  science  has  yet  done  very 
little  towards  investigating  the  nature  of  the  different  compounds. 
In  the  chemical  laboratories,  carburets  of  iron  are  generally  made 
by  decomposing  in  a  high  heat  the  salts  of  iron  of  the  vegetable 
acids;  we  obtain  in  that  way  various  compositions,  whose  nature  is 
not  investigated.  Those  compounds  of  iron  and  carbon  deserve 
more  attention  on  the  part  of  scientific  men  than  has  yet  been  paid 
to  them.  The  investigations  of  such  men  would  enable  us  to 
understand  the  nature  of  pig  metal  better  than  we  do  at  present. 

Some  ores,  of  which  we  are  at  present  ignorant,  may  belong  to 
the  class  of  carburets;  they  are  certainly  not  found  in  the  older 
rocks,  but  from  the  period  of  the  coal  measures  to  the  present  we  may 
expect  to  find  them.  We  are  not  aware  that  there  are  any  employed 
in  the  United  States  in  the  manufacture  of  iron,  but,  where  such  can 
be  found  they  deserve  to  be  employed.  In  Scotland,  the  whole  iron 
business  depends  mainly  upon  this  kind  of  ore ;  there  it  is  called 
Blackband,  and  was  first  made  use  of  by  Mr.  Mushet  at  the  com- 
mencement of  the  present  century.  After  encountering  great  oppo- 
sition, this  ore  enables  Scotland  to  be  master  in  every  pig  iron 
market  which  she  can  supply. 

Carburets  are  black,  sometimes  grayish,  of  slaty  appearance, 
more  or  less  hard,  but  always  harder  than  clay  slate  ;  the  powder  is 
attracted  by  the  magnet,  and  turns  brown  or  red  by  being  calcined. 
Some  varieties  burn  in  larger  heaps  without  other  fuel ;  others  have 
to  be  calcined,  by  adding  coal  or  wood.  Foreign  matter  is  almost 
always  mixed  with  the  ore ;  these  admixtures  are  mainly  silex  or 
clay.  Frequently  this  ore  is  classed  with  the  magnetic  oxide,  on 
account  of  its  black  color  ;  but  it  is  soluble  in  sulphuric  acid,  and 
with  the  escape  of  hydrogen  leaves  carbon,  which  distinguishes  it 
from  the  black  magnetic  ore. 

In  the  coal  deposits  of  Frostburgh  (Md.),  this  ore  is  found  of  an 
inferior  quality ;  it  generally  contains  but  from  20  to  25  per  cent, 
of  iron.  It  is  also  found  in  small  quantities  in  the  Pittsburgh  coal 
formation. 

This  ore  deserves  the  attention  of  the  iron  master ;  for,  if  even 


24  MANUFACTURE    OF   IRON. 

poor,  it  always  furnishes  good  pig  metal,  and  is,  after  being  well 
roasted,  an  excellent  material  in  the  blast  furnace :  it  is  more  in- 
clined to  make  gray  foundry  iron  than  any  other  ore  ;  besides  that, 
it  works  exceedingly  well  in  the  furnace. 

IV.  Sulphurets  of  Iron. 

Iron  has  a  very  great  affinity  for  sulphur,  and  we  are  acquainted 
with  five  definite  compounds.  It  is  very  difficult  to  separate  iron 
from  sulphur  by  heat  alone.  Of  the  five  different  compositions,  two 
only  deserve  our  attention — the  white  and  the  yellow  sulphurets. 

a.  White  Sulphur et  of  Iron. —  White  Pyrites  abound  in  coal  beds, 
and  in  the  accompanying  strata  of  clay;  also  in  regular  veins  along 
with  ores  of  lead,  copper  and  iron,  in  the  transition  rocks.     They 
are  very  common  all  over  the  globe ; .  and  are  found  in  New  York, 
Massachusetts,  Connecticut,  Ohio,  and  other  States.     Before  the 
blowpipe,  sulphuret  of  iron  becomes  red ;  upon  charcoal,  the  sul- 
phur is  evaporated,  and  oxide  of  iron  remains ;  it  is  very  liable  to 
decomposition.     It  is  preferable  to  the  yellow  kind  in  the  manufac- 
ture of  copperas,  and  is,  in  coal  mines,  the  most  dangerous  of  any, 
for  it  often  decomposes  so  quickly  as  to  kindle  the  coal  slack.  There- 
fore, where  it  is  frequently  met  with  in  coal  mines,  great  cleanliness 
and  order  ought  to  be  practiced.     Its  composition  is,  in  100  parts, 

45.07  iron 
53.35  sulphur 
0.58  manganese 

99.00  white  pyrites. 

b.  Yellow  Sulphuret  of  Iron.     Yellow  Pyrites. — This  variety 
becomes  red  before  the  blowpipe,  like  the  above ;  in  the  reducing 
flame  it  melts  into  a  globule,  which  continues  red-hot  for  a  short 
time,  and  possesses,  after  cooling,  a  crystalline  appearance.     In 
nitric  acid,  it  is  slowly  soluble  with  the  precipitation  of  sulphur, 
but  in  no  other  acid.     It  is  composed  of 

47.30  iron 
52.70  sulphur 

100.00  yellow  sulphuret  of  iron. 

Yellow  pyrites  is  almost  identical  with  the  white  pyrites,  and  the 
latter  appears  to  be  only  different  in  containing  more  foreign  matter. 
Both  are  widely  diffused  among  the  ores  of  iron.  We  find  such  in 


IRON   ORE.  25 

massive  nodules,  crystals,  and  veins,  in  the  coal  beds,  clay  slate, 
graywacke,  greenstone,  limestone,  and  in  beds  in  primitive  slate. 
It  is  the  main  material  which  is  used  for  manufacturing  copperas, 
alum,  oil  of  vitriol,  and  Spanish  brown,  sulphur,  and  sulphuric  acid. 

In  the  United  States,  we  find  iron  pyrites  in  Vermont,  New  York, 
Ohio,  New  Jersey,  Pennsylvania,  Maryland,  and,  in  fact,  more  or 
less  in  every  State. 

This  class  of  Iron  compound  does  not  belong  to  the  iron  ores 
proper,  but  its  immense  quantity,  and  its  presence  in  coal  beds, 
require  especial  notice,  on  account  of  the  injurious  effect  it  has 
upon  the  quality  of  iron,  where  it  comes  in  contact  with  the  ores 
or  coal.  The  presence  of  pyrites  is  generally  indicated  by  its 
sulphurous  smell,  either  in  roasting  the  ore  or  in  the  casting  house ; 
and  when  such  indication  is  manifest,  the  careful  roasting  of  the 
ores,  and  the  long  exposure  of  the  roasted  ore  to  the  atmosphere, 
are  the  best  methods  of  removing  the  sulphur.  If  the  main  body 
of  sulphur  is  found  to  be  in  the  fuel,  there  is  little  hope  of  getting 
rid  of  it,  for  it  cannot  be  entirely  expelled  where  a  surplus  of  carbon 
is  present,  as  is  the  case  in  caking  coal. 

Y.  Phosphurets  of  Iron. 

Phosphorus  combines  readily  with  iron  ;  the  compound  is  whiter 
than  iron  itself,  can  be  beautifully  polished,  but  is  very  brittle, 
cold-short.  Native  phosphurets  are  very  seldom  found,  and  we  allude 
to  them  because  the  presence  of  phosphorus  in  the  pig  metal  occa- 
sions it  to  be  cold-short.  Under  the  head  of  phosphate  of  iron  we 
shall  speak  of  the  ores  belonging  to  this  class. 

VI.  Arseniurets  of  Iron. 

A  native  compound  of  iron,  arsenic,  and  sulphur,  is  called  mis- 
pick  el  ,  or,  if  it  contains  silver,  which  is  often  the  case,  it  is  deno- 
minated argentiferous  arsenical  iron.  Arsenic  and  iron  have  con- 
siderable affinity,  and  in  smelting  combine  readily  ;  the  composition 
is  brittle,  not  magnetic.  Mispickel  is  white,  hard,  of  a  vitreous 
lustre;  it  emits  before  the  blowpipe  arsenical  fumes,  and  leaves  asul- 
phuret  of  iron  and  arsenic  soluble  in  nitric  acid,  and  is  composed  of 

36.04  iron 

42.88  arsenic 

21.08  sulphur 

100.00  mispickel. 


26  MANUFACTURE   OF   IRON. 

In  Germany  it  is  used  for  the  manufacture  of  arsenious  acid,  and 
is  sometimes  mixed  with  iron  ores ;  but  it  is  very  apt  to  choke  the 
top  of  the  blast  furnace,  for  the  arsenic,  evaporating  in  the  greater 
heat  of  the  hearth,  condenses  at  the  cooler  top. 

The  most  interesting  deposits  of  this  ore  are  in  the  United  States; 
at  Franconia,  N.  H.,  Worcester,  Mass.,  and  Chatham,  Conn. 

A  small  quantity  of  this  material,  mixed  with  the  other  iron  ores, 
does  no  harm  to  the  product ;  a  larger  quantity  occasions  it  to  be 
cold-short,  and  is  troublesome  in  the  blast  furnace. 

VII.  Chlorides  of  Iron. 

Chloride  of  iron  should  hardly  be  ranged  among  the  ores  of  iron, 
but  in  many  respects  it  deserves  our  attention.  Chlorides  are  fre- 
quently found  among  the  iron  ores  of  the  hydrates  as  a  chloride  of 
iron,  or  of  sodium,  and  in  some  other  unimportant  combinations ; 
their  presence  is  unquestionable.  We  find  indications  of  chlorine 
on  the  top  of  burnt  ore  piles,  and  in  the  wash-water  of  iron  ores. 
Chlorides  are  seldom  or  never  found  in  the  more  ancient  deposits, 
and  occur  only  in  the  hydrates,  or  brown  iron  ore.  Their  pre- 
sence in  smaller  quantities  is  very  favorable,  and  promotes  the 
operations  in  the  blast  furnace ;  it  accelerates  the  motion  of  the 
charges,  and  furnishes  a  liquid,  lively  cinder.  Such  ores  are  very 
apt  to  furnish  gray  iron,  of  an  excellent  quality  for  the  forge,  though 
generally  too  cold-short  for  the  foundry.  Larger  quantities  of  chlo- 
rides occasion  trouble  in  the  blast  furnace,  and  produce  white  pig 
metal ;  but  the  metal  is  always  of  good  quality. 

VIII.  Sulphates  of  Iron. 

Sulphuric  acid  has  great  affinity  for  the  oxides  of  iron,  and  can 
with  difficulty  be  entirely  separated  from  such.  Neither  heat  nor 
strong  alkalies  separate  the  oxide  Q_f  iron  from  the  sulphuric  acid,  and 
under  all  circumstances  a  part  of  the  acid  is  left  in  an  oxide  or  iron 
ore,  where  it  is  combined.  Iron  masters  are  not  very  apt  to  make 
use  of  the  sulphates  of  iron,  either  as  green,  white,  or  red  copperas ; 
but  in  that  large  body  of  iron  ores,  the  hydrates,  particularly  those 
of  the  coal  formation,  there  is  more  or  less  sulphuric  acid  mixed 
with  the  ore ;  and,  as  this  acid  cannot  be  expelled  entirely  by 
heat,  it  is  a  dangerous  enemy  to  the  manufacturer.  Whether  sul- 
phuric acid  is,  or  is  not,  in  the  ore,  can  be  ascertained  by  pounding, 
and  heating  it  to  redness  along  with  some  filings  of  wrought  iron, 


IRON   ORE.  27 

and  by  dissolving  the  protosulphate  which  is  formed  in  water; 
that  is,  wash  the  whole  mass  in  rain  water,  and  test  with  chloride 
of  barium  for  sulphuric  acid.  Sulphuric  acid  is  generally  found 
in  the  yellow  hydrates,  but  may  be  observed  in  the  whole  class  of 
hydrates. 

The  great  disadvantage  arising  from  sulphuric  acid  in  iron  ores, 
is  its  indestructibility  by  heat;  and  if,  besides  heat,  carbon  is  pre- 
sent, then  the  sulphuric  acid  is  decomposed,  and  leaves  sulphuret 
of  iron.  This  happens  either  in  the  calcining  process,  or  in  the 
blast  furnace,  and  on  that  account  sulphuric  acid  acts  in  the  same 
manner  as  sulphur  itself,  or  pyrites,  and  occasions  hot-short  iron. 

IX.  Phosphate  of  Iron. 

*  Phosphate  of  iron,  green  iron  ore,  is  of  a  dull  blue  color,  and 
turns  yellowish-brown  before  the  blowpipe;  or, in  the  reducing  flame, 
into  a  black,  porous  slag;  it  is  not  magnetic,  and  it  is  soluble  in 
hydrochloric  acid.  It  is  often  dark  lake  green,  and  of  a  vitreous, 
silky  lustre. 

Its  composition  is,  in  100  parts, 

62.52  oxide  of  iron 
28.50  phosphoric  acid 
8.98  water 


100.00  phosphate  of  iron. 

This  ore  is  seldom  found  in  large  masses,  but  frequently  inter- 
spersed in  other  ores,  and  for  that  reason  we  take  notice  of  it.  It 
occurs  in  small  particles  of  aggregated  plates,  sometimes  only  visible 
by  means  of  a  microscope.  Generally,  this  phosphate  is  mixed 
with  the  yellow  hydrates,  fossiliferous  and  bog  ores,  and  is  the 
cause  of  very  cold-short  iron;  and  on  this  account  is,  if  not  to  be 
rejected,  at  least  to  be  regarded  with  great  suspicion.  Still,  the 
ores  of  this  kind  have  one  great  advantage — that  is,  of  furnishing  a 
cheaper  iron  than  that  from  all  the  other  ores;  the  phosphorus  can 
be  completely  removed  in  the  puddling  furnace.  Where  such  ore 
occurs,  it  is  generally  in  large  bodies,  and  can  be  easily  wrought; 
so  that  the  price  of  the  ore  is  not  to  be  considered  an  objection 
to  it.  It  is,  of  all  classes  of  ore,  the  best  in  the  blast  furnace, 
and  consumes  less  fuel  than  any  other  kind.  Where  forges  are 
in  such  a  condition  as  to  work  the  cold-short  metal  into  saleable 
bar  iron,  or  into  any  particular  form,  it  is,  beyond  question,  the 


28  MANUFACTURE    OF  IRON. 

most  available.     In  the  course  of  this  work  we  shall  have  oppor- 
tunities to  refer  to  this  subject  again. 

In  Europe,  particularly  in  the  plains  of  Russia  and  Prussia,  there 
are  immense  masses  of  bog  ore,  from  which  large  quantities  of  iron 
are  manufactured.  These  ores  contain  more  or  less  of  the  phosphate, 
and  the  iron  produced  is  cold-short.  In  the  United  States,  we  believe, 
there  is  but  little  of  this  ore ;  Michigan  and  Ohio  contain  it  in 
small  quantity.  There  may  be  bog  ore  in  Alabama,  Arkansas,  and 
Florida:  but  the  fossiliferous  ore  of  Pennsylvania  and  Maryland 
contains  phosphate  of  iron. 

X.  Carbonate  of  Iron. 

Sparry  Iron;  Brown  Spar. — This  most  important  species  contains 
two  varieties;  the  spathose,  or  sparry  iron  ore,  and  the  compact' 
carbonate. 

a.  Sparry,  or  Spathic  Iron,  Steel  Iron  Ore,  is  of  a  lamellar  sparry 
fracture.  Color,  yellowish-gray,  Isabella,  or  even  brownish-red; 
turns  brown  before  the  blowpipe,  and  is  then  attracted  by  the 
magnet.  After  being  taken  from  the  mine,  it  assumes  a  brown  tint 
by  exposure  to  the  atmosphere;  gives  a  slight  effervescence  with 
nitric  acid,  and  changes  to  a  brown  color.  Manganese  and  mag- 
nesia, as  well  as  carbonate  of  lime,  are  frequently  found  mixed  with 
it.  It  melts  into  a  green  glass  with  borax. 

Its  composition  varies,  but  a  specimen  from  Europe  contained 
63.75  protoxide  of  iron 
34.00  carbonic  acid 
0.75  oxide  of  manganese 
0.72  magnesia 
0.78  lime  and  water 


100.00  sparry  iron  ore. 

Sparry  carbonate  belongs  to  the  primitive  formation,  forming  vast 
veins  and  layers  in  gneiss  and  primitive  slate  and  limestone;  it  is 
associated  with  quartz,  copper  pyrites,  gray  copper,  fibrous  brown 
oxide  of  iron,  and  carbonate  of  lime.  Beds  of  immense  quantities 
are  found  in  Styria,  forming  at  Eisenerz  a  mountain  as  high  as  the 
snow  line,  from  which  ore  was  dug  by  the  ancient  Romans.  These 
beds  appear  inexhaustible.  In  Carinthia  an  excellent  ore  of  this 
kind  exists,  from  which  iron  and  steel  of  the  first  quality  are  pro- 
duced. In  fact,  most  of  the  iron  and  steel  of  Austria  is  derived 


IRON   ORE.  29 

from  this  ore.  It  is  distributed  all  over  Germany ;  and  the  cheap, 
though  celebrated,  German  steel  is  manufactured  from  sparry  iron 
ore.  The  cutlery  and  weapons  of  Solingen,  in  Western  Germany, 
are  made  from  iron  and  steel  of  the  sparry  ore,  which  is  dug  in 
Siegen,  occurring  in  heavy  veins  and  beds  in  transition  slate.  This 
ore  is  found  in  France,  England,  Scotland,  Russia,  Spain,  Switzer- 
land, and  various  other  countries. 

A  very  considerable  vein  of  spathic  iron  is  found  near  Roxbury, 
Conn.,  traversing  a  vein  of  quartz,  imbedded  in  gneiss;  also  in 
Plymouth,  Vt. ;  and  in  small  quantity  in  Monroe,  Conn. 

This  is  a  very  valuable  and  interesting  species.  It  affords  steel 
with  the  greatest  facility,  and  is  one  of  the  most  favorable  ores  in 
the  Catalonian  forge.  By  proper  treatment,  it  produces  an  excel- 
lent kind  of  bar  iron,  which  is  sufficiently  esteemed  by  the  black- 
smith. 

b.  The  Compact  Carbonate  of  Iron — spherosiderite  argillaceous 
iron  ore — has  no  relation  externally  with  the  sparry  variety ;  it  com- 
prehends most  of  the  clay  iron  stones  of  the  coal  measures,  parti- 
cularly those  which  occur  in  flattened  spheroidal  masses,  varying 
in  size  from  the  dimensions  of  a  small  bean  to  pieces  weighing  a 
ton.  The  color  of  this  ore  is  commonly  a  dirty  blue  or  gray,  brown, 
reddish-brown  and  yellowish-brown.  Fracture  close-grained,  hard, 
streaked  white  or  brown.  Blackens  before  the  blowpipe,  and,  if  cal- 
cined, is  attracted  by  the  magnet. 

This  carbonate  of  iron,  though  belonging  to  the  coal  formation, 
is  found  in  various  places  in  the  tertiary  strata.  It  is  the  prin- 
cipal ore  from  which  iron  is  smelted  in  England  and  Scotland, 
and  yields  usually  from  30  to  33  per  cent,  of  metal.  It  is  largely 
distributed  over  the  United  States.  Pennsylvania  abounds  in  it. 
It  exists  in  Maryland,  Virginia,  Ohio,  Illinois,  North  Carolina,  and 
Kentucky.  The  difficulty  of  working  this  kind  of  ore  in  the  blast 
furnace,  of  which  we  shall  speak  in  another  chapter,  maybe  assigned 
as  the  reason  why  it  is  not  more  generally  in  use.  England  and 
Scotland  use  it  extensively,  and  work  scarcely  any  other  kind. 

Prof.  Rogers,  in  his  Reports  of  the  Geology  of  Pennsylvania, 
has  given  a  great  many  analyses  of  argillaceous  ores,  of  which  we 
shall  select  the  following  : — 


30  MANUFACTURE   OF   IRON. 

In  100  parts  of  ore  were  found  : 

53.03  protoxide  of  iron 
35. IT  carbonic  acid 

3.33  lime 

1.77  magnesia 

1.40  silica 
0.63  alumina 

0.23  peroxide  of  iron 
3.03  bitumen 

1.41  water 

100.00  argillaceous  ore. 

This  may  be  considered  an  analysis  of  one  of  the  best  specimens. 
Generally  these  ores  contain  no  more  than  30  per  cent,  of  iron ;  and 
an  average  of  the  argillaceous  ores  of  the  Pennsylvania  and  Mary- 
land coal  measures  would  not  go  farther  than  25  per  cent.  The 
compact  carbonates  afford  with  charcoal  and  cold  blast  an  excellent 
forge  iron;  by  the  hot  blast  the  quality  is  greatly  injured;  but  if 
properly  calcined,  and  the  burden  not  too  heavy,  it  forms  an  excellent 
gray  foundry  metal.  Still  the  operations  in  the  yard,  of  roasting 
and  those  of  the  blast  furnace,  are  somewhat  difficult,  particularly 
for  those  who  are  not  very  experienced  founders,  and  acquainted 
by  practice  with  this  kind  of  ore.  In  the  chapter  on  blast  furnaces 
we  will  refer  to  this  subject. 

XL  Titanate  of  Iron. 

Titaniferous  Iron,  Iron  Sand,  is  an  oxide  of  iron  and  titanic  acid, 
and  belongs  to  the  class  of  the  magnetic  oxides.  It  is  attracted  by 
the  magnet,  is  of  a  deep  black  color,  metallic  lustre,  very  hard,  and 
perfectly  opaque;  melts  into  a  black  slag  by  a  high  temperature. 
It  is  generally  found  near  volcanoes  or  volcanic  rocks,  but  seldom 
in  quantities  sufficient  to  justify  the  erection  of  iron  works;  never- 
theless, the  quality  is  mostly  good,  and  the  volcanic  regions  around 
the  lakes  may  present,  in  the  course  of  time,  encouraging  prospects. 

There  are  two  classes  of  iron  ore  which  do  not  belong  properly 
to  our  department,  but  are  interesting  as  well  on  account  of  their 
belonging  to  the  United  States  alone,  as  on  account  of  their  large 
quantity  and  usefulness.  For  this  reason  we  shall  notice  them. 


IRON   ORE.  31 

XII.  Chromate  of  Iron. 

Chrome  ore,  or  chromated  iron  ore,  is  infusible  before  the  blow- 
pipe; acts  upon  the  magnet  after  being  roasted ;  of  difficult  smelt- 
ing with  borax. 

Its  composition,  in  100  parts,  is 

43.00  oxide  of  chrome 
34.70  protoxide  of  iron 
20.30  alumina 
2.00  silica 

100.00  chromedron. 

Chrome  ore  is  found  in  serpentine  and  cotemporanequs  rocks,  in 
irregular  veins  and  beds.  It  is  found  in  Europe;  but  in  largest 
quantity  within  the  United  States;  at  the  Bare  Hills,  near  Baltimore; 
at  Hoboken,  New  Jersey,  and  at  Milford  and  West  Haven,  Conn. 
Europe  derives  its  supply  from  these  places. 

XIII.  Franklinite. 

DodecaTiedral  Iron  Ore. — Color  black,  and  behaves  before  the 
blowpipe  like  the  black  magnetic  ore :  but  with  alkalies  in  the  re- 
duction fire,  it  emits  fumes  of  white  oxide  of  zinc,  and  becomes 
green.  It  is  composed  of 

66.00  peroxide  of  iron 
16.00  red  oxide  of  manganese 
17.00  oxide  of  zinc. 

Franklinite  is  found  near  Franklin  furnace,  in  Hamburg,  New 
Jersey,  accompanied  by  another  variety  of  zinc  ore,  in  large  veins  and 
masses ;  it  is  a  species  belonging  to  North  America  alone. 

XIY.   G-eneral  Remarks. 

The  ores  of  iron  are  distributed  over  the  whole  globe  in  great 
profusion.  They  are  found  in  every  latitude  and  in  every  climate. 
But  every  mineral  which  contains  iron  does  not  constitute  an  iron 
ore.  The  consideration  of  quality  and  quantity  determines  the 
application  of  a  mineral  species  to  the  manufacture  of  iron.  The 
basis  upon  which  our  arguments  in  this  case  rest,  is  the  general 
theory  of  reducing  metals,  and  the  experience  of  old  establishments. 

We  will  proceed  to  define  the  general  theory,  and  to  illustrate 
that  theory  by  facts. 


32  MANUFACTURE   OF   IRON. 

a.  Theory  of  Reducing  Ores  to  Metals. — The  metals,  with  the 
exception  of  gold,  silver,  and  copper,  are  seldom  found  in  their 
native  state.     They  are  combined  with  other  matter  in  their  native 
beds,  and  it  is  the  study  of  the  metallurgist,  by  dissolving  this 
combination,  to  reduce  them  to  their  simple  condition.    The  matters 
thus  combined,  are  oxygen,  sulphur,  carbon,  chlorine,  and  phos- 
phorus ;  and  combinations  of  the  oxides  of  metals  with  the  acids  of 
the  above  metalloids. 

b.  Metals  and  Oxygen. — Metals,  particularly  iron,  combine  very 
readily  with  oxygen,  and  form  oxides.     In  the  combinations  of  iron 
with  oxygen,  there  are  four  distinct  grades ;  the  first  is  one  atom  of 
iron  with  one  atom  of  oxygen,  or  FO,*  the  protoxide.    The  second, 
two  atoms  of  iron  with  three  atoms  of  oxygen,  F203,  or  the  peroxide. 
The  third  is  a  combination  of  one  atom  of  the  protoxide  with  one 
atom  of  the  peroxide,  FO-f  F203,  the  magnetic  oxide ;  and  the  fourth, 
one  atom  of  iron  with  three  atoms  of  oxygen,  or  the  ferric  acid. 
The  latter  is  a  production  of  the  chemical  laboratory,  and  is  beyond 
the  limits  of  our  labors. 

The  affinity  of  the  metals  for  oxygen  is  different  in  different  metals, 
and  varies  with  the  temperatures  under  which  the  combinations  are 
formed.  Some  are  oxidized  by  a  temperature  below  freezing,  as 
potassium  or  manganium :  others  by  the  medium  temperature,  as 
zinc,  tin,  lead,  iron,  &c.  Some  cannot  be  oxidized  by  the  atmo- 
sphere at  all,  as  gold,  platina,  silver.  Most  of  the  metals  can  be 
combined  with  oxygen  by  being  dissolved  in  nitric  acid,  or  nitro- 
muriatic  acid  (aqua  regia).  Some  metals  decompose  water  readily ; 
such  are  potassium,  sodium,  and  the  metals  of  the  alkalies  gene- 
rally ;  but  iron  and  zinc  decompose  water  slowly.  If,  however, 
an  acid  be  added  to  the  water  which  dissolves  the  oxide  formed, 
the  decomposition  of  water  goes  on  rapidly.  In  all  these  instances 
the  oxygen  of  the  water  is  absorbed  by  the  metal,  and  the  hydrogen 
liberated.  Some  metals  cannot  be  oxidized  by  means  of  acids,  nor 
directly  by  the  atmosphere,  as  rhodium  and  iridium,  but  oxidize 
very  easily  by  being  previously  melted  together  with  potash  or  salt- 
petre. Chrome,  and  a  few  others,  are  of  this  kind. 

Noble  metals  are  those  which  are  not  oxidized  by  heat  and  ac- 
cess of  oxygen.  To  this  class  belong  gold,  platina,  silver,  iridium. 
Another  class  of  metals  are  oxidized  in  the  heat  of  a  flame,  but 
lose  their  oxygen  in  higher  temperatures ;  such  as  palladium, 

*  F  for  ferrum  (iron),  and  0  for  oxygen. 


IRON    ORE.  33 

rhodium,  quicksilver,  nickel,  and  lead.     All  other  metals,  when 
heated  with  access  of  the  atmosphere,  absorb  oxygen  and  retain  it. 

When  a  metal  combines  with  oxygen,  it  loses  its  metallic,  and 
assumes  an  earthy  appearance,  sometimes  of  a  white,  or  black 
color.  For  this  reason  the  old  chemists  applied  to  the  oxides  of 
metals  the  term  calc — that  is,  resembling  alkaline  earth.  This 
idea  is  worthy  of  notice,  for  most  of  the  oxides  of  the  metals  are 
electro-positive,  while  but  few  are  electro-negative.  This  sub- 
ject is  of  great  importance  in  metallurgy,  and  deserves  attention. 
Metals  whose  oxides  are  mainly  electro-positive  are  gold,  osmium, 
iridium,  platinum,  rhodium,  silver,  mercury,  uranium,  copper, 
bismuth,  tin,  lead,  cadmium,  zinc,  nickel,  cobalt,  iron,  manganese, 
and  cerium.  These  are  at  least  four  times  heavier  than  water ; 
very  few  are  oxidized  at  common  temperatures  of  the  atmosphere, 
but  all  can  be  deoxidized  by  means  of  carbon. 

Metals  whose  oxides  are  mainly  electro-negative,  are  selenium, 
tellurium,  arsenic,  chrome,  vanadium,  molybdenum,  wolfram,  anti- 
mony, and  titanium.  The  oxides  of  these  metals  take  the  place 
of  acids,  and  form,  with  the  above  oxides  and  the  alkalies  proper, 
salts  of  definite  proportions. 

Metals  which  form  with  oxygen  the  alkalies  proper,  are  potas- 
sium, sodium,  lithium,  barium,  strontium,  calcium,  magnesium, 
aluminum,  beryllium,  yttrium,  zirconium,  and  thorium. 

We  should  be  cautious  not  to  conclude  that  this  classification  of 
the  oxides  of  metals  into  electro-negative  and  electro-positive,  is 
absolutely  or  literally  true,  for  most  metals  have  oxides  of  different 
composition ;  combine  with  one,  two,  three,  five,  or  seven  atoms 
of  oxygen,  and  are  in  that  proportion  more  or  less  alkaline  or  acid. 
The  oxides  of  potassium  and  zinc  are  always  electro-positive  to 
those  oxides  whose  metals  are  negative  to  potassium  and  zinc. 
Sometimes,  in  fact,  the  first  oxide  of  a  metal  is  an  alkali,  and  the 
second  an  acid ;  this  is  the  case  with  the  oxides  of  tin  and  man- 
ganese, and  also  with  iron.  The  protoxide  of  iron  is  a  strong 
alkali,  and  its  peroxide  so  much  of  an  acid,  that  both  combine  and 
form  a  distinct  salt,  with  all  the  characters  of  neutralization,  the 
magnetic  oxide.  We  intend  to  refer  to  this  subject  in  the  theory 
of  fluxes. 

c.  Hydrates. — Oxides  of  metals  form  definite  compounds  with 
water,  and  are  then  called  hydrates.     The  water  in  the  hydrates  of 
potash  and  clay  is  so  strongly  combined  with  its  base,  that  the 
3 


34  MANUFACTURE   OF   IRON. 

strongest  heat  is  hardly  sufficient  to  separate  them.  Other  hy- 
drates are  easily  decomposed,  as  the  hydrate  of  iron ;  while  a  few 
are  decomposed  in  boiling  water.  Hydrates  always  decompose 
and  combine  more  readily  than  the  oxides. 

d.  Reduction  of  Oxides. — Most  of  the  oxides  of  metals  can  be 
decomposed,  that  is,  the  metal  revived  by  means  of  carbon,  under 
various  conditions ;  which  conditions  we  will  explain  more  particu- 
larly in  the  chapter  on  reviving  iron.     There  is  a  great  difference, 
however,  in  the  affinity  of  oxygen  for  metals,  and  that  may  be 
assigned  as  a  cause  of  their  different  behavior  with  carbon  ;  but  the 
main  cause  is,  undoubtedly,  the  aggregate  form  of  the  oxide  :  for 
carbon  is  strong  enough  to  separate  potassium  and  oxygen,  and 
why  not  silicon  and  oxygen,  or  aluminum  and  oxygen  ?     The  cohe- 
sion of  the  atoms  of  these  oxides  is  so  strong,  that  the  particles,  or 
congregation  of  atoms,  which  the  oxides  form,  resist  in  a  body  the 
affinity  of  carbon  for  oxygen.     We  find  this  general  law  of  the  dif- 
ficult decomposition  of  particles,  particularly  applicable  to  the 
oxides  of  iron.     The  solutions  of  the  peroxide  salts  of  iron  are  very 
easily  reduced  to  protoxide  salts,  but  with  great  difficulty  to  metal; 
It  appears,  therefore,  that  the  oxygen  is  more  firmly  connected  to 
the  metal  in  the  protoxide  than  in  the  peroxide,  or,  that  the  atoms 
of  the  protoxide  are  more  inclined  to  crystallization.     Most  of  the 
other  oxides  follow  the  same  law,  and  very  few  the  reverse.     To 
the  latter  belong  mercury  and  tin.     According  to  this   general 
theory,  the  more  oxygen  the  metal  absorbs,  that  is,  the  higher  the 
state  of  oxidation,  the  more  readily  will  oxides  be  reduced  to  me- 
tals.    This  theory  is  confirmed  by  experience  at  the  blast  furnace, 
for  we  know  by  practice  that  magnetic  oxide  is  disadvantageous  in 
its  raw  state,  and  that  it  is  far  better  after  being  roasted  or  oxid- 
ized.    The  most  favorable  condition  of  iron  ore  for  the  blast  fur- 
nace is  the  peroxide  of  iron,  the  reason  of  which  we  will  explain, 
hereafter;  and  if  we  cannot  find  native  peroxides,  we  must  pro- 
duce such  by  art — that  is,  by  roasting  and  calcining — in  the  cheap- 
est and  most  practicable  manner. 

e.  Reviving  of  Metals. — To  illustrate  the  foregoing  principle 
more  fully,  it  will  be  best  to  explain  the  reviving  of  metals  in  each 
particular  case.     This  will  furnish  practical  proof  that  the  reduc- 
tion of  the  oxides  is  the  more  complete,  the  higher  the  state  of  oxida- 
tion ;  it  will  also  prove  that  oxides  are  the  material  from  which 
metals  can  be  most  conveniently  derived. 


IRON   ORE.  35 

Potassium  is  produced  by  mixing  the  oxides  with  carbon  and 
heat,  or,  more  imperfectly,  by  heating  the  hydrated  oxide  of  potas- 
sium along  with  metallic  iron. 

Sodium  is  revived  by  the  same  means  as  potassium,  but  it  is  not 
so  easily  evaporated  as  potassium,  and  requires  more  heat.  It  re- 
vives more  readily  if  the  oxide  of  sodium  is  mixed  with  hydrated 
oxide  of  potassium. 

The  metals  of  the  alkaline  earths,  barium,  strontium,  calcium, 
cannot  be  reduced  by  means  of  carbon,  because  the  metals  are 
more  permanent,  and  resist  evaporation.  The  oxides  of  these 
metals  are  reduced  by  means  of  electricity. 

Magnesium,  Aluminum,  Beryllium,  Crlucinum,  Yttrium,  cannot 
be  revived  by  direct  application  of  carbon.  The  best  way  of  pro- 
ducing these  metals  is  by  melting  their  chlorides  together  with 
potassium. 

Tellurium  and  Arsenic  can  be  made  by  exposing  their  hyper- 
oxides,  mixed  with  carbon,  to  ignition. 

Chrome  and  Vanadium  are  revived  from  their  oxides  and  hyper- 
oxides  by  mixing  the  oxides  with  carbon  and  igniting  the  mass. 

Molybdenum,  Wolfram  or  Tungsten,  may  be  easily  revived  from 
their  oxides  by  means  of  carbon. 

Antimony  and  Zirconium  are  not  so  easily  revived  from  their 
combinations ;  they  require  some  skilful  manipulations. 

Titanium  can  be  revived  from  titanic  acid  by  means  of  carbon. 
It  requires  a  high  heat  to  melt  it. 

Crold  can  be  revived  from  its  oxide  by  mere  heat;  of  course  more 
readily  by  adding  carbon. 

Osmium,  Iridium,  Platinum,  Palladium,  Rhodium,  have  very 
little  affinity  for  oxygen,  and  of  course  are  easily  revived. 

Silver,  Mercury,  Uranium,  Bismuth,  are  very  easily  revived 
from  their  oxides  by  means  of  carbon. 

Copper,  Tin,  Lead,  Zinc,  are  produced  by  exposing  their  oxides, 
mixed  with  carbon,  to  a  red  heat. 

Nickel,  Cobalt,  Iron,  Manganese,  Cerium,  are  easily  revived  from 
their  oxides,  but  require  a  somewhat  strong  heat. 

We  here  observe  that  experience  proves  the  oxides  are  the  most 
available  for  the  production  of  metals  from  their  combinations,  and  of 
this  fact  we  must  not  lose  sight,  for  it  not  only  justifies  the  roasting 
of  ores,  but  shows  that  to  be  both  necessary  and  economical.  The 
perfect  oxides  alone,  that  is,  the  red  oxides  of  iron,  should  be  sent  to 
the  furnace  in  their  raw  state.  We  will  describe  the  most  common 


36  MANUFACTURE    OF  IRON. 

combination  of  the  metals  with  other  matters,  and  in  that  way  shall 
arrive  at  the  safest  means  to  convert  such  combinations  into  oxides. 

/.  Metals  and  Sulphur. — Metals  combine  very  readily  with  sul- 
phur, and  such  combinations  are  called  sulphurets.  Iron  espe- 
cially has  great  affinity  for  sulphur,  and  does  not  part  with  it  even 
in  the  highest  heat.  The  process  by  which  sulphur  combines  with 
metals,  is  analogous  to  the  process  by  which  oxygen  combines  with 
them.  Sulphurets  burn;  they  emit  light  and  heat;  and,  in  all 
their  chemical  properties,  are  almost  identical  with  the  oxides. 
They  are  distinguished  from  the  oxides  by  their  metallic  lustre. 
They  are  sometimes  translucent,  as,  for  instance,  sulphurets  of 
mercury  and  zinc.  Very  few  sulphurets  can  be  reduced  by  carbon ; 
but  almost  all  of  them  by  adding  alkalies,  or  a  metal  which  has  a 
stronger  affinity  for  sulphur.  This  is  the  case  with  the  sulphurets 
of  copper  and  lead.  If  these  are  melted,  and  metallic  iron  added, 
the  iron  will  combine  with  the  sulphur  and  revive  the  metals. 
Metallic  oxides  are  reduced  to  sulphurets  by  adding  sulphuretted 
hydrogen,  or  sulphuretted  carbon;  and  perhaps  this  is  the  mani- 
pulation by  which,  in  the  laboratory  of  nature,  where  sulphuretted 
hydrogen  abounds,  metallic  oxides  are  daily  reduced.  Sulphurets 
can  be  reduced  by  heating  them  in  an  atmosphere  of  hydrogen ;  by 
which  means  sulphuretted  hydrogen  is  formed;  this  application, 
however,  is  very  limited,  and  does  not  apply  to  iron  or  copper. 
The  most  common  way  to  reduce  the  sulphurets,  is  to  transform 
them  into  oxides,  and  then  to  reduce  the  oxides.  This  is  most  safely 
done  in  the  chemical  laboratory. 

Sulphurets  are  transformed  into  oxides  by  roasting  and  calcining. 
The  material  should  be  pounded  to  powder,  and  then  heated  with 
access  of  the  atmosphere.  Great  care  should  be  taken  that  the  mass 
does  not  melt ;  for  if  this  happens,  the  operation  is  a  failure,  and 
must  be  repeated.  The  largest  quantity  of  sulphur  escapes  as  sul- 
phurous gas;  and  the  metal  remains  in  the  highest  state  of  oxi- 
dation. One  part  of  the  sulphur  is  generally  converted  into  sul- 
phuric acid,  and  remains  with  the  oxide;  another  part  remains  with 
the  metal,  and  is  detected  by  adding  an  acid.  This  especially 
happens  with  the  sulphuret  of  iron.  Such  remains  of  sulphur  can 
be  removed  by  adding  alkalies,  or  washing  with  water,  the  latter  of 
which  extracts  the  sulphates  and  carries  them  off;  but  in  case  a 
part  of  the  sulphur  is  left  in  the  form  of  sulphuret,  the  whole  mass 
should  be  roasted  until  it  is  properly  oxidized.  One  way  of  con- 


IRON   ORE.  37 

verting  the  sulphurets  into  oxides,  is  very  important,  and  deserves 
attention.  As  above  mentioned,  some  metals  are  not  very  easily 
converted  into  oxides ;  to  effect  this  conversion,  we  should  melt 
them  together  with  alkalies,  or  with  oxidized  bodies  which  have  a 
great  affinity  for  water.  This  law  applies  equally  well  to  the 
sulphurets.  Sulphurets  are,  like  the  metals,  very  compact,  and 
their  atoms  are  not  exposed  to  the  influence  of  oxygen  or  any  other 
matter  unless  when  dissolved.  If  we  melt  the  sulphurets  together 
with  alkalies,  which,  besides  dissolving  most  sulphurets,  have  a 
great  affinity  for  water,  the  aggregate  form  of  the  sulphurets  is  de- 
stroyed, and  the  atoms  offer  their  poles  to  the  poles  of  other  matter; 
and  if  heated  in  the  meantime,  most  of  the  sulphur  is  expelled  either 
as  sulphurous  acid  or  sulphuretted  hydrogen.  The  rest  of  the  sul- 
phur is  generally  converted  into  sulphuric  acid,  and  remains  with 
the  alkali.  Barytes  and  lime  are  in  this  case  powerful  agencies  ; 
more  powerful  than  even  the  alkalies.  The  more  permanent  sul- 
phurets, melted  together  with  chloride  of  sodium,  are  very  quickly 
transformed  into  oxides.  All  other  salts  will  act  in  the  same  way ; 
and  nitrates  even  better  than  chlorides;  but  nitric  acid  is  not  so 
permanent  as  chlorine,  and  would  be  more  expensive.  This  beha- 
vior of  the  sulphurets  with  alkalies  and  the  salts,  is  particularly 
applicable  to  iron,  and  may  be  productive  of  benefit  to  the  careful 
manipulator. 

If  we  consider  the  great  affinity  of  the  metals  for  sulphur,  par- 
ticularly iron,  whose  affinity  is  very  strong,  and  consider  further  the 
injurious  effects  of  sulphur  upon  iron,  we  shall  be  very  cautious  in 
preparing  and  selecting  our  ores,  for  it  frequently  happens  that  sul- 
phur exists  in  ore  where  we  least' suspect  it;  it  is  not  only  injurious 
to  the  metal,  but  to  the  manipulation  in  the  blast  furnace.  We 
should,  therefore,  pay  attention  to  the  perfect  oxidation  of  the  ores, 
before  we  make  any  use  of  them.  When  describing  the  manipula- 
tion in  roasting  ores,  we  shall  allude  to  this  subject  again. 

g.  Metals  and  Phosphorus. — Most  metals  combine  readily  with 
phosphorus,  especially  iron,  though  not  so  readily  as  with  sulphur. 
Carbon  is  necessary,  in  almost  every  case,  to  produce  a  combina- 
tion of  phosphorus  with  metal.  Phosphorus  is  easily  expelled  by 
roasting  a  phosphuret  without  carbon ;  but  if  carbon  is  present,  the 
phosphorus  adheres  very  strongly  to  the  metal,  and  its  evaporation 
is  difficult.  Just  so  it  is  with  sulphur,  for  the  same  manipulation 
which  removes  sulphur  will  remove  phosphorus.  Phosphorus  pre- 
sents to  us  no  greater  difficulties  than  sulphur.  The  main  difference 


38  MANUFACTURE    OF   IRON. 

between  them  is  the  different  effect  they  have  upon  iron ;  sulphur 
makes  iron  hot-short,  and  phosphorus  cold-short:  but  phosphorus  is 
advantageous  in  the  blast  furnace;  the  reverse  is  the  case  with 
sulphur. 

h.  Metals  and  Carbon;  Carburets. — Iron,  lead,  and  potassium 
have  great  affinities  for  carbon ;  but  if  simply  carburets  of  iron  are 
to  be  smelted,  the  expulsion  of  carbon  may  be  easily  effected  by 
roasting  the  ore. 

i.  Metals  and  Acids  frequently  exist  in  native  ores.  The  Halo- 
gen combinations  of  chlorine,  bromine,  iodine,  fluor,  are  either  eva- 
porated, or  combine  mostly  with  the  oxides,  that  is,  the  alkalies, 
whose  metals  are  to  be  smelted;  they  are  never  injurious.  Sul- 
phates are  more  dangerous,  for  the  sulphuric  acid  is,  in  the  presence 
of  carbon,  decomposed,  and  leaves  the  sulphur  in  connection  with 
the  metal.  This  remark  applies  equally  to  Phosphates.  Nitrates  are 
not  in  the  least  dangerous ;  for  a  small  heat,  with  the  presence  of 
carbon,  decomposes  them.  Carbonates  sometimes  require  a  strong 
heat,  as  well  as  a  long  time,  to  be  decomposed,  which  is  particularly 
the  case  with  iron;  and  as  carbonates  are  most  generally  protosalts, 
we  never  get  the  higher  oxides  directly.  This  makes  the  roasting  of 
carbonates  of  iron  very  difficult;  for,  if  the  heat  is  strong  enough  to 
expel  the  carbonic  acid,  it  is  generally  strong  enough  to  melt  the 
magnetic  oxide,  or  the  protoxide,  together  with  foreign  matter. 
Borates  are  injurious  to  the  metal,  but  very  advantageous  in  the 
furnace.  Silicates  are  directly  of  no  use,  particularly  those  of  iron, 
but  may  be  converted  into  oxides  by  being  melted  with  alkalies, 
and  then  oxidized.  Tellurates,  Arseniates,  Antimoniates,  Wolf- 
ramiates,  Titanates,  and  Manganates,  are  very  easily  converted  into 
oxides,  and  but  slightly  injurious  in  the  manufacture  of  iron.  We 
meet  with  the  whole  of  these  compounds  of  metals  and  acids  in  the 
native  hydrates  of  the  oxides,  for  in  case  the  ore  or  hydrate  is  a 
decomposition  of  a  salt,  the  acid  is  never  entirely  removed  ;  and 
should  either  of  the  above  acids  have  access  in  any  way  to  an  oxide 
of  iron,  we  shall  surely  detect  it  in  the  hydrate.  Of  all  the  hydrates, 
that  of  iron  is  the  most  apt  to  retain  acids,  partly  on  account  of  its 
electro-positive  character,  but  mainly  on  account  of  its  forming  a 
great  variety  of  basic  compounds,  which  are  more  or  less  difficult 
of  solution.  Such  basic  salts  are  then  mechanically  mixed  with  the 
hydrates,  and  are  the  cause  of  forming  hydrates  from  the  oxides  of 
iron.  By  all  means,  therefore,  hydrates  should  be  roasted. 


IRON   ORE.  39 


XV.  Roasting  of  Iron  Ore. 

"Whether  an  iron  ore  should  be  roasted,  is  a  question  which  very 
seldom  arises ;  at  least  this  question  seldom  ought  to  arise.  With 
the  exception  of  the  red  impalpable  oxide,  the  whole  body  of  iron 
ores  require  roasting ;  even  the  specular  iron  ore,  if  it  is  very  com- 
pact ;  but  the  best  oxide,  if  too  compact,  works  badly  in  the  fur- 
nace. All  other  ores  should  be  subjected  to  calcination.  Some  iron 
masters  are  in  the  habit  of  using  the  hydrates  raw,  but  this  should 
not  be  done  where  clay  ores  are  smelted,  for  these  tend  to  blacken 
the  tuyere ;  or  where  the  hydrates  contain  either  chlorides  or  phos- 
phates. In  the  latter  case,  the  pig  metal  will  be  cold-short,  if  there 
is  too  much  phosphorus.  Under  all  circumstances,  however,  it  is 
best  to  roast  the  ores  if  we  expect  good  metal  and  well-regulated 
furnace  operations. 

The  object  of  roasting  ores  is  either  to  produce  higher  oxidation, 
or  to  expel  injurious  admixtures.  In  both  cases,  liberal  access  of 
atmospheric  air  is  required ;  we  should,  therefore,  so  arrange  our 
roasting  operations,  as  to  fulfil  these  conditions,  from  which  it  will 
appear  that  different  ores  require  different  treatment.  To  explain 
this  more  fully,  we  shall  take  a  review  of  the  various  ores. 

a.  Magnetic  Oxide  of  Iron. — This  ore  is  very  compact,  heavy, 
and  of  an  almost  metallic  appearance  ;  to  open  the  textures  of  the 
ore,  to  make  it  more  porous,  lighter,  and  to  oxidize  it  more  highly, 
it  should  be  roasted  ;  sulphur  is  frequently  combined  with  it.     This 
ore  melts  into  a  slag  by  a  cherry-red  heat ;  we  should,  therefore, 
avoid  a  high  heat,  for  a  melted  clinker  is  useless  and  injurious  in 
the  blast  furnace,  and  a  melted  mass  cannot  be  oxidized  by  common 
means. 

b.  Hydrated  Oxide  of  Iron,  Brown  Oxide,  Hematite,  Bog  Ore. — 
This  whole  class  ought  to  be  roasted,  not  for  the  purpose  of  oxida- 
tion, but  in  order  to  drive  off  the  acids,  and  destroy  sulphurets  and 
phosphurets,  for  all  the  ores  of  this  class  contain  more  or  less  in- 
jurious matter.     This  ore  will  bear  a  high  temperature  in  roasting, 
if  there  is  no  foreign  matter  mixed  with  it ;  but  of  this  it  is  very 
seldom  free. 

c.  Carburets  of  Iron  are  to  be  roasted,  partly  on  account  of  the 
sulphur  which  they  frequently  contain,  and  partly  for  the  expulsion 
of  the  hydrogen  which  is  generally  combined  with  the  carbon. 
The  roasting  of  this  ore  is  easily  effected. 


40  MANUFACTURE   OF  IRON. 

d.  Sulphurets  of  Iron. — These,  of  course,  require  roasting,  if 
designed  for  the  manufacture  of  iron  ;  the  manipulation  is  difficult, 
and  requires  more  than  usual  attention  and  time. 

e.  Phosphurets  of  Iron,  where  they  happen  to  be  mixed  with  the 
oxides,  should  be  roasted,  if  we  expect  medium  qualities  of  iron ; 
but  if  the  quality  is  no  object,  and  cheapness  the  aim,  then  phos- 
phurets,  in  their  raw  condition,  will  answer. 

/.  Arseniurets  of  Iron. — If  iron  ores  contain  arsenic,  it  is  best  to 
roast  them ;  arsenic  does  not  injure  the  metal ;  but  if  the  top  or  shaft 
of  the  blast  furnace  works  cool,  there  is  sometimes  danger  of  chok- 
ing at  the  top,  or  of  scaffolding  at  the  lining  above  the  boshes. 

g.  Chlorine  contained  in  iron  ore  does  no  harm  whatever,  and 
may  be  considered  beneficial  in  roasting. 

h.  Sulphates  of  Iron  should  be  carefully  roasted  with  liberal  ac- 
cess of  air.  This  will  apply  also  to 

i.  Phosphates. 

Jc.  Carbonates  require  careful  treatment.  In  the  furnace  they 
melt  before  carbon  has -any  influence  upon  them  ;  and  if  there  is  any 
admixture  of  foreign  matter,  the  carbonates  are  very  apt  to  pro- 
duce but  a  small  quantity  of  white  iron,  with  black  cinder.  The 
roasting  of  carbonates  is  difficult ;  the  best  means  of  roasting  them 
are,  low  heat,  and,  if  possible,  access  of  watery  vapors,  partly  to 
carry  off  the  heavy  carbonic  acid  gas,  and  partly  to  prevent  a  too 
high  temperature ;  for,  if  the  heat  is  too  strong,  the  carbonate  melts 
together  with  the  oxide,  and  forms  a  black  cinder. 

All  other  ores  are  easily  calcined ;  they  require  no  particular 
attention. 

It  is  evident  that,  as  the  qualities  of  these  ores  are  different,  they 
should  require  different  treatment ;  and  the  question  which  meets 
us  is,  what  arrangement,  in  each  particular  case,  will  best  enable 
us  to  arrive  at  the  highest  perfection.  For  roasting  ores,  there 
are  three  distinct  modes  of  manipulation — ovens,  piles,  and  rows. 
Each  arrangement  may  be  considered  perfect  for  a  particular  kind 
of  ore  ;  but  each  is  not  equally  applicable  to  all  varieties  of  ore. 
We  must  modify  our  manipulations  according  to  circumstances,  in 
order  to  produce  appropriate  results. 

Under  all  circumstances  the  ore  to  be  roasted  should  be  broken 
into  pieces  as  small  as  those  usually  put  into  the  blast  furnace,  say 
two  or  three  inches  ;  if  we  neglect  this,  of  course  we  cannot  expect 
a  good  result,  for  it  is  obvious  that  large  pieces  will  not  receive 
heat  and  oxygen  through  their  whole  body  so  soon  as  smaller  pieces; 


IRON   ORE. 


41 


and  as  the  main  object  is  oxidation,  no  means  should  be  neglected 
which  will  accomplish  the  end  in  view.  The  kind  of  fuel  required 
is  not  of  so  much  consequence  as  it  is  usually  thought  to  be  at 
charcoal  furnaces.  Wood  and  small  charcoal  (braise)  are  used  ;  but 
where  wood  is  scarce,  stone  coal,  properly  applied,  will  answer ; 
coke  or  anthracite  is  preferable.  Bad  or  sulphurous  coal  should  be 
avoided,  or  at  least  coked  before  used.  Turf  or  peat,  or  brown  coal 
may  be  used,  where  they  can  be  obtained  upon  advantageous  terms. 

aa.  Roasting  of  Iron  Ore  in  Ovens  or  Furnaces. — There  are 
many  different  forms  of  ovens,  but  all  of  them  can  be  reduced  to 
that  of  the  blast  furnace,  or  the  limekiln.  They  are  either  per- 
petual, or  work  by  charges. 

These  ovens  are  commonly  from  twelve  to  eighteen  feet  high,  and 
contain  from  fifty  to  one  hundred  tons  of  ore  at  once.  Fig.  1  re- 
presents such  an  oven  for  perpetual  work :  a  is  the  shaft  or  circular 


Fig.  1. 


Section  of  a  roast-oven. 

hearth,  where  ore  and  fuel  are  thrown  in  ;  5,  b  are  the  grate  bars, 
which  can  be  removed  to  let  down  the  roasted  ore  ;  c,  c  are  side 
arches,  which  permit  access  to  the  draft  holes  :  d,  d,  d,  d  are  four 
arches,  including  the  work  arch.  To  start  operations  in  such  an 
oven,  the  grate  bars  are  covered  with  wood  ;  upon  this  either  small 


42 


MANUFACTURE   OF  IRON. 


charcoal,  or  stone  coal,  coke,  turf,  brown  coal,  or  any  fuel  fit  for 
the  purpose,  is  placed  ;  then  a  layer  of  coal  and  ore  alternately, 
until  the  oven  is  filled,  after  which  the  fire  is  kindled.  When  the 
lower  portions  of  ore  are  sufficiently  roasted  and  cool,  they  are  ta- 
ken out,  and  either  carried  to  the  furnace,  or,  in  case  the  ore  is  not 
sufficiently  roasted,  returned  to  the  top.  The  air  holes  d,  d,  d,  d 
are  designed  to  admit  air  when  it  is  needed,  and  to  enable  us  to 
observe  the  progress  of  the  work.  An  oven  of  fifty  tons  capacity 
ought  to  yield  thirty  tons  of  well  roasted  ore  in  twenty-four  hours ; 
but  this  depends  very  much  on  circumstances,  and  especially  upon 
the  quality  of  ore  to  be  roasted.  As  the  top  of  the  ore  sinks,  it  is 
replaced  by  fresh  charges  of  coal  and  ore.  This  oven  is  well 
qualified  to  roast  the  hydrates,  carburets,  and  other  easily  worked 
ores ;  but  will  not  answer  for  carbonates,  sulphurets,  or  even  mag- 
netic ore,  for  these  ores  are  too  soon  melted. 

In  some  parts  of  Europe,  another  kind  of  oven  is  in  use,  which 
affords  a  better  product  than  the  perpetual  oven,  and  may  be  em- 
ployed with  great  advantage.  This  oven  is  represented  by  Fig.  2. 
Its  interior  is  a  cone,  wide  at  the  base,  and  narrow  at  the  top.  At 

Fig.  2. 


Section  of  an  ore  roasting  oven. 

the  bottom  of  this  cone  an  arch  of  coarse  pieces  of  iron  ore  is  built, 
which  supports  the  body  of  ore  charged  above  it.  This  arch  will 
admit  enough  fuel  to  keep  up  a  lively  fire.  Where  wood  is  plenty, 
it  may  be  used  in  its  green  state,  but  any  other  fuel  will  answer 
quite  as  well.  One  great  advantage  which  this  arrangement  has 


IRON   ORE. 


43 


over  the  other  (Fig.  1),  is  that  it  does  not  bring  the  fuel  into  con- 
tact with  the  ore  ;  and  the  workmen  are  enabled  to  give  just  so 
much  heat  as  they  consider  necessary.  Such  an  oven,  properly 
managed,  may  answer  for  any  kind  of  ore,  provided  it  be  suffi- 
ciently coarse  to  admit  the  draft  of  air  needed  for  oxidation.  Though 
this  arrangement  makes  manipulating  more  expensive  than  the  ar- 
rangement first  presented,  yet  the  qualitative  properties  of  the  pro- 
duct which  it  furnishes — for  there  is  no  doubt  that  a  good  workman 
will  deliver  a  more  perfectly  oxidized  ore  from  this  kiln  than  from 
the  other — more  than  compensate  for  this  expense. 

An  improvement  upon  this  principle  has  been  made  in  Sweden 
and  Norway  by  erecting  large  circular  ovens,  like  porcelain  kilns, 
at  the  base  of  which,  in  furnaces  built  around,  or  in  the  centre 
of  the  oven,  the  fire  is  applied.  Such  an  arrangement  will  work 
continuously,  like  that  of  Fig.  1,  but  is  expensive  both  in  the  first 
outlay,  and  in  the  operation.  Reverberatory  furnaces  have  been 
tried  for  roasting  ores,  but  with  little  success ;  the  operation  proved 
too  expensive. 

bb.  Roasting  in  Mounds. — Sulphurets  and  carbonates,  which 
cannot  bear  a  high  heat,  and  require  sometimes  several  fires,  are 
best  roasted  in  mounds.  Mounds  are  formed  on  a  level  ground,  and 
consist  of  three  stone  or  brick  walls:  see  Fig.  3.  The  area  or 


Fig.  3. 


Ground  plan  of  a  roasting  mound. 

hearth  is  open  on  one  side,  so  as  to  admit  the  entrance  of  wheel- 
barrows or  carts :  the  walls  are  about  three  feet  high,  and  have  at 
their  bases  fire  chambers,  where  the  fuel  is  applied.  This  is  shown 
at  a,  a,  a,  a,  Fig.  4.  Through  the  piled  ore  are  draft  holes  or  chim- 
neys, 5,  ft,  which  regulate  the  draft;  by  these  chimmeys,  the  draft 
may  be  altogether  stopped  when  the  ore  gets  too  hot.  This  kind 


44  MANUFACTURE   OF  IRON. 

of  oven  or  mound  is  very  useful  for  small  ores,  and  those  which 
cannot  bear  much  heat. 

Fig.  4. 


Z 


Section  of  an  ore  roasting  mound. 

cc.  Roasting  in  the  Open  Air  in  Heaps. — This  mode  of  calcining 
ore  is  undoubtedly  the  most  available,  and  that  generally  practiced. 
It  affords  by  good  management  excellent  results.  To  form  a  heap, 
or  heaps,  the  ground  must  be  leveled,  and  in  many  cases  covered 
with  beaten  clay.  The  area  of  such  a  level  depends  entirely  on  the 
amount  of  ore  to  be  roasted,  and  the  time  in  which  it  is  proposed  to 
be  done.  It  may  be  laid  down  as  a  rule,  that  the  longer  the  fire 
remains  in  a  pile,  or  the  slower  the  roasting  is  carried  on,  the  better 
will  be  the  result.  If  the  time  is  limited,  rows  of  three  feet  high, 
from  seven  to  eight  feet  wide  at  the  base,  and  of  convenient  length, 
may  be  put  up  and  fired.  These  rows  may  be  finished  in  ten  or 
twelve  days  ;  but  though  they  answer  well  enough  for  hydrates, 
sulphurets,  carburets,  and  all  those  ores  which  calcine  easily,  they 
do  not  answer  for  magnetic  ore  or  carbonates.  For  those  ores  which 
are  roasted  with  difficulty,  round  or  square  piles  of  various  dimen- 
sions are  used ;  some  of  these  piles  have  a  capacity  of  from  one 
hundred  to  two  thousand  tons.  The  amount  of  ore  in  fire  should 
depend  mainly  on  the  stock  on  hand,  and  on  the  quality  of  the  ore. 
Magnetic  ore  may  be  roasted  in  the  course  of  six  or  eight  weeks ; 
argillaceous  ores  of  the  blue  or  gray  kind,  require  at  least  three 
months;  and  the  sparry  carbonates  can  scarcely  be  roasted  in  one 
heat,  frequently  require  different  fires,  and,  after  all,  are  but  seldom 
sufficiently  calcined.  In  Styria,  Carinthia,  and  other  places  where 
heavy  sparry  iron  ore  abounds,  and  where  good  iron  must  be  de- 
livered, the  iron  masters  are  compelled  to  have  a  stock  of  ore  suffi- 
cient to  supply  the  furnace  for  a  number  of  years,  and  the  compli- 


IRON    ORE.  45 

cated  manipulations  by  which  the  sparry  carbonates  are  oxidized, 
often  require  a  period  of  from  three  to  five  years.  The  operation  is 
there  mainly  conducted  on  the  principle  of  oxidizing  by  the  influ- 
ence of  the  atmosphere  ;  for  that  purpose  the  ores  are  broken  into 
small  fragments  of  the  size  of  walnuts,  then  spread  upon  level  plains, 
in  a  thin  stratum  of  about  two  inches  thick,  and  then  exposed  to 
the  action  of  the  sun  and  atmosphere  ;  in  dry  weather  the  ores  are 
sprinkled  with  water  once  or  twice  every  day.  Ores  oxidized  in 
this  way  are,  of  course,  far  superior  to  those  oxidized  by  means  of 
artificial  heat.  The  method  of  roasting  ore  in  the  open  air  by  ar- 
tificial heat  is  as  follows :  Billets  of  wood  are  placed,  like  the  bars 
of  a  gridiron,  upon  a  previously  prepared  level  spot ;  sometimes  they 
are  laid  parallel,  and  sometimes  in  a  crosswise  manner,  so  as  to 
form  a  uniform  flat  bed.  The  crevices  between  the  wood  may  be 
filled  with  chips  of  wood,  charcoal,  turf,  or  even  stone  coal,  coke, 
or  anthracite,  so  as  to  prevent  the  ore  from  falling  between  the 
other  pieces  of  fuel,  or,  what  is  still  worse,  upon  the  ground.  The 
ore,  before  it  is  put  upon  the  fuel,  should  be  broken  into  pieces  of 
uniform  size,  of  from  three  to  four  inches  in  diameter ;  the  larger 
pieces  to  be  used  inside  of  the  pile,  the  smaller  ones  for  covering. 
When  a  foundation  of  fuel  of  about  eight  inches  high  is  prepared, 
ore  may  be  piled  upon  it  to  the  height  of  from  eighteen  inches  to 
two  feet ;  upon  this  ore  is  spread  a  layer  of  small  charcoal,  or  of  turf, 
coke,  or  small  anthracite  coal,  in  a  uniform  thickness  of  two  inches, 
or  one  inch  of  fuel  to  one  foot  of  ore  ;  then  alternate  beds  of  fuel 
and  ore,  until  a  sufficient  height  is  reached.  The  pile,  thus  prepared, 
whether  of  an  oblong,  square,  or  round  form,  should  be  covered 
with  small  ore,  and  then  should  be  set  on  fire  either  in  the  centre — 
for  which  purpose  one  or  more  holes  or  flues  are  left — or  around  the 
base.  After  the  fires  are  properly  kindled,  the  piles  may  be  covered 
with  riddlings  of  ore  or  small  coal.  The  combustion  should  pro- 
ceed slowly,  being  somewhat  suffocated,  so  that  the  whole  mass  may 
be  uniformly  penetrated  with  heat.  Where  the  fire  is  too  intense, 
it  must  be  covered  with  small  ore  or  coal  dust,  and  where  it  is  too 
imperfectly  developed,  holes  should  be  pierced  with  an  iron  bar, 
that  smoke  and  air  may  have  vent. 

In  all  cases  of  calcining  in  heaps,  the  arrangement  and  manipu- 
lation are  almost  the  same,  with  hardly  any  other  variations  than 
those  arising  from  the  difference  of  ore  and  fuel.  Fig.  5  represents 
the  cross  section  of  an  ore  pile,  which  is  so  plain  as  to  need  no 
description.  In  this  plan  the  billets  of  wood  are  raised  from  the 


46  MANUFACTURE   OF  IRON. 

Fig.  5. 


Section  of  an  ore  heap  ready  for  firing. 

ground,  which  affords  the  advantage  of  enabling  us  to  kindle  the 
pile  wherever  we  choose. 

XVI.   Gleaning  of  Roasted  Ores. 

Iron  ores,  after  being  roasted,  are  very  apt  to  be  mixed  with  foreign 
matter.  This  must  be  separated  from  them.  The  usual  method 
of  accomplishing  this,  is  as  follows :  A  movable  screen,  made  of  a 
wooden  frame,  filled  with  iron  bars  from  one-fourth  to  three-eighths 
of  an  inch  in  diameter,  leaving  one-fourth  of  an  inch  space  between 
the  bars,  is  put  close  to  the  ore  pile.  The  dry  ores  are  thrown  by 
means  of  shovels  against  the  iron  bars,  when  the  fine  ores  and  fine 
dust  pass  through  the  spaces  between  the  bars  of  the  screen,  and 
the  coarse  ore  rolls  before  the  screen  to  the  feet  of  the  workman. 
Stones  and  coarse  foreign  matter  may  be  separated  by  hand ;  the 
fine  riddlings  are  thrown  aside,  or  may  be  used  for  leveling  the  ore 
yard ;  mixed  with  lime,  they  make  an  excellent  mortar. 

A  more  convenient,  though  more  complicated  contrivance  than 
the  above,  is  the  following.  It  is  in  general  use.  A  strong  wooden 
frame-work,  made  of  oak  scantling  five  inches  thick,  contains  the 
screen  a,  Fig.  6,  made  in  the  usual  way  of  round  iron  bars  from 
one-fourth  to  three-eighths  of  an  inch  in  diameter,  separated  from 
each  other  by  one-fourth  of  an  inch  space.  It  is  a  kind  of  flat  box  ; 
the  bottom  b  is  formed  of  the  iron  rods.  This  box  is  suspended 
on  wires,  at  four  points  c  <?,  which  permit  a  swinging  motion  of  the 
screen.  If  a  shovelful  of  ore  is  thrown  into  the  screen  «,  5,  d, 
and  a  boy,  standing  by/,  moves  the  screen  back  and  forwards,  the 
coarse  ore  will  roll  into  the  box  or  wheelbarrow  e,  and  the  riddlings 
or  fine  matter  will  accumulate  in  g,  below  the  screen  ;  h  is  a  cross- 


Machine  for  cleaning  ore. 

piece  fastened  to  the  screen,  which,  by  constantly  striking  against 
the  frame,  occasions  a  more  lively  motion  of  the  ore.  This  simple 
machine  answers  all  that  is  required  in  screening,  and  is  a  useful 
fixture.  The  ores,  when  screened,  should  be  cleaned  by  hand,  that 
stones  and  lumps  of  other  foreign  matter  may  be  removed. 

The  screenings  or  riddlings  contain  a  large  amount  of  ore,  which 
is  generally  lost.  Where  this  is  valuable,  and  where  the  particles 
of  the  ore  in  the  screenings  are  coarse,  a  great  deal  of  it  may  be 
regained  by  washing  the  dust.  Calcareous  ores,  or  ores  originally 
mixed  with  lime,  clay,  and  common  earth,  in  fact,  all  those  screen- 
ings whose  admixtures  are  sufficiently  fine  to  be  carried  off  by  a 
current  of  water,  may  be  advantageously  washed,  and  the  greater 
part  of  the  ore  thus  recovered;  but  fine  earthy  ore  dust  cannot  be 
saved  in  that  way.  The  washing  of  this  ore  is  generally  effected 
in  wooden  troughs,  where,  by  letting  a  continual  stream  of  clear 
water  flow  upon  the  ore,  and  by  repeatedly  stirring  the  mass,  the 
fine  dust  of  lime  or  clay  is  loosened  and  carried  off.  This  mani- 
pulation can  be  applied  where  the  price  of  ore  is  sufficiently  high 
to  justify  the  expenses  of  the  labor  bestowed  upon  it. 

XVII.   Theory  of  Roasting  Ores. 

There  is  a  variety  of  opinions  on  this  subject,  and  iron  masters 
by  no  means  agree  in  relation  to  it.  Some  consider  the  manipula- 
tions mainly  designed  for  the  expulsion  of  sulphur,  but  if  this  were 
the  case,  all  those  ores  free  from  sulphur  would  require  no  roasting 
at  all.  But  all  agree  that  the  operation  of  roasting  is  necessary. 


48  MANUFACTURE  OF   IRON. 

Others  regard  the  operation  as  exclusively  a  manipulation  of  oxida- 
tion, without  reference  to  anything  else ;  but  we  find  that  even  the 
highest  peroxides  sometimes  require  roasting.  We  shall  arrive  at 
the  true  solution  of  this  question  in  a  future  chapter.  We  will 
confine  ourselves  at  present  to  the  most  important  part,  or,  the 
practical  view,  of  the  operation.  The  object  of  the  manipulation 
of  roasting  or  calcining  may  be  considered  mainly  that  of  oxida- 
tion, for  a  heat  sufficiently  strong  to  oxidize  ore,  expels  all  other 
volatile  matter ;  and  the  iron  retains  oxygen  alone.  All  matter 
generally  found  in  iron  ore,  which  is  considered  injurious  to  the 
metal,  is  more  or  less  volatile,  and  expelled  by  a  cherry-red  heat ; 
for  instance,  sulphur,  phosphorus,  chlorine,  arsenic,  antimony, 
sulphuric  acid,  phosphoric  acid,  carbonic  acid,  &c. ;  but  copper, 
and  silver  can  not  be  expelled,  and  ores  which  contain  these 
metals  must  be  rejected  altogether.  Therefore,  by  oxidizing  the 
ore,  we  at  once  free  it  from  all  injurious  ingredients,  and  on  that 
account  we  should  pay  particular  attention  to  the  means  by  which 
metals,  particularly  iron,  are  oxidized.  This  subject  has  been 
investigated  at  page  32,  and  it  is  only  necessary  to  speak  here 
more  especially  upon  the  oxidation  of  iron. 

Iron  corrodes,  that  is,  oxidizes,  very  readily,  but  faster  in  a  moist 
than  in  a  dry  atmosphere ;  more  rapidly  by  the  presence  of  an  acid 
than  an  alkali ;  more  quickly  when  divided  into  small  particles,  than 
in  solid  masses.  If  we  apply  these  laws  to  the  present  case,  we  shall 
find  that  the  breaking  of  the  ore  is  advantageous ;  that  the  presence 
of  some  water  is  very  beneficial;  and  that  the  burning  of  the  fuel 
ought  to  be  so  far  perfected  as  to  form  carbonic  acid,  but  not  to  suffo- 
cate the  fire,  and  thus  form  carbonic  oxide,  which  is  an  alkali.  In 
applying  this  theory,  we  shall  find  that  we  ought  to  break  the  ore  into 
lumps  of  uniform  size ;  roast  the  ore,  when  possible,  by  wood  and 
charcoal,  which  generates  steam  and  carbonic  acid  more  readily 
than  any  other  fuel ;  and  establish  our  ore  yard  on  a  moist  ground, 
that  a  continual  current  of  watery  vapors  may  thus  pass  through 
the  hot  ore  pile.  The  method  of  oxidizing  metals,  indicated  at 
page  37,  can  scarcely  be  applied  to  iron  ores,  because  it  is  too  ex- 
pensive ;  but,  as  it  possesses  decided  advantages  in  some  cases, 
we  have  alluded  to  it. 

XVIII.  Mixing  of  Ores. 

A  mere  practical  rule  will  not  suffice  to  indicate  the  method  of 
conducting  this  very  important  operation.  A  scientific  demonstra- 


IRON  ORE.  49 

tion  is  required  to  enable  us  to  understand  this  subject  fully.  We 
shall  more  particularly  refer  to  it  under  the  theory  of  the  blast 
furnace. 

XIX.  Practical  Remarks. 

Upon  the  quality  and  price  of  iron  ores  the  success  of  an  iron 
manufactory  mainly  depends;  and  these  ores  should  be  considered 
in  every  relation  before  a  dollar  is  invested  in  any  improvements, 
of  whatever  nature.  In  the  United  States,  the  manufacture  of  iron 
presents  greater  comparative  advantages  than  in  Europe  and  other 
parts  of  the  world,  so  far  as  the  natural  deposits,  ore  and  mineral 
coal,  are  concerned;  nevertheless,  great  caution  is  required  before 
a  working  plan  is  set  in  motion.  It  is  true,  native  material  is  more 
abundant,  and  of  better  quality,  in  the  United  States,  than  anywhere 
else ;  but  labor  is  more  valuable ;  and,  therefore,  in  no  part  of  the 
world  are  so  much  attention,  industry,  and  intellect  required  to  carry 
on  iron  establishments.  The  cost  of  iron  is,  to  a  greater  degree 
than  in  any  other  manufacture,  represented  by  wages,  paid  by  a 
single  manufacturer;  therefore,  great  responsibility  rests  upon  those 
who  engage  individually  in  such  an  enterprise. 

The  quality  and  quantity  of  the  ore  greatly  affect  the  prosperity  of 
the  local,  as  well  as  that  of  the  general  iron  business.  Its  quality  may 
be  improved  by  scientific  knowledge;  its  quantity  by  industry:  but 
where  this  knowledge  is  wanting,  the  rule  is,  never  to  venture  upon 
the  working  of  bad  or  strange  ores.  Where  this  rule  is  disregarded, 
failure  in  the  first  instance  is  attended  by  failure  in  all  the  subse- 
quent manipulations  of  the  manufacture.  This  frequently  occasions 
losses  to  the  producer  which  he  is  unable  to  bear,  and  brings  ruin 
upon  individuals  who  deserve  a  better  fate.  Ores,  whose  qualities 
are  not  yet  known,  should  be  treated  with  the  utmost  caution, 
and  we  should  use  every  means  to  investigate  their  nature  before 
we  enter  into  extensive  operations.  In  fact,  until  we  feel  perfectly 
safe,  these  operations  should  either  be  suspended,  or  abandoned 
altogether,  for  the  first  is  generally  the  smallest  loss.  Ores  of 
acknowledged  good  quality  are  generally  so  far  removed  as  not  to 
afford  an  easy  market,  or  so  much  cultivated  that  the  profits  derived 
from  working  them  are  small ;  or  are  attended  by  other  disad- 
vantages. In  all  cases,  it  is  safer  to  start  business  with  good  ores 
than  to  run  the  risk  of  an  experiment.  If  the  profits  are  small, 
the  consolation  of  sustaining  no  loss  is  at  least  a  great  benefit. 
4 


50  MANUFACTURE  OF  IRON. 

We  shall  take  a  short  review  of  the  different  kinds  of  ore  which 
the  United  States  afford  to  the  manufacturer. 

a.  Magnetic  Oxide  of  Iron. — Black  magnetic  ore  is  found,  in  the 
State  of  New  York,  on  Lake  Champlain  and  Hudson  River;  in  Ver- 
mont, at  Bridgewater  and  Marlborough  ;  in  New  Hampshire,  at 
Franconia;  in  New  Jersey  and  Pennsylvania,  in  large  quantities;  in 
Missouri  and  Wisconsin ;  and  will  doubtless  be  found  in  Oregon, 
California,  and  New  Mexico.  This  ore  is  generally  rich  ;  and  one 
ton  and  three-quarters  to  three  tons  of  ore  produce?  on  an  average, 
one  ton  of  metal.  It  very  seldom  affords  cheap  pig  metal,  on  ac- 
count of  the  expense  of  roasting  it,  and  of  working  it  in  the  blast 
furnace.  If  we  want  a  good  quality  of  pig  metal  from  this  ore,  it 
must  be  carefully  roasted,  and  under  all  conditions  worked  by  cold 
blast  in  the  furnace.  By  proper  treatment,  it  affords  the  very  best 
and  safest  kind  of  bar  iron  ;  but  by  carelessness,  or  by  an  inju- 
dicious saving  of  fuel,  very  short,  brittle  iron.  By  careful  roasting, 
and  the  cold  blast,  Sweden  and  Russia  furnish  excellent  iron ;  but 
all  experiments  of  raw  mine  and  hot  blast  have,  thus  far,  failed  to 
produce  from  this  ore  a  quality  of  iron  favorable  to  the  market. 
Where  we  want  good  bar  or  wrought  iron,  and  are  not  too  parti- 
cular in  relation  to  expense,  this  ore  may  furnish  a  solid  founda- 
tion for  a  prosperous  business. 

5.  The  next  in  quality  is  the  Sparry  Carbonate  of  Iron.  This- 
is  seldom  found  in  the  United  States ;  it  exists  in  Roxbury  and 
Monroe,  Conn.,  and  Plymouth,  Vermont,  but  in  quantities  too  small 
to  deserve  particular  attention.  Spathic  ore  is  the  most  expensive 
material  from  which  iron  is  manufactured,  on  account  of  the  various 
and  expensive  manipulations  which  the  production  of  a  good  mar- 
ketable article  renders  necessary  ;  gray  pig  metal  it  will  scarcely 
yield  by  any  means,  and  the  application  of  hot  blast  is  so  injurious 
to  its  quality,  that  all  experiments  have  yet  failed  to  make  that 
modern  improvement  available.  But  by  careful  treatment  of  the 
ores,  cold  blast  in  the  furnace,  and  proper  manipulation  in  the  forges, 
this  ore  yields  a  bar  iron  unsurpassed  in  strength,  and  furnishes  steel 
with  extraordinary  facility. 

c.  Specular  Iron  Ore. — This  class,  so  far  as  we  are  acquainted 
with  the  deposits  of  iron  ore,  is  very  scarce  in  the  United  States. 
In  Massachusetts  and  New  York,  there  is  hardly  any  worth  men- 
tioning ;  but  according  to  the  geological  formations  of  Iowa,  Mis- 
souri, Arkansas,  Texas,  Oregon,  California,  and  New  Mexico,  these 
States  ought  to  contain  specular  ore.  This  ore  is,  in  many  respects, 


IRON   ORE.  51 

the  most  valuable  of  any ;  for  its'  application  is  very  simple,  and  the 
iron  it  yields  is  the  strongest  and  most  tenacious  kind  known  in  the 
world.  Where  it  can  be  bought  at  reasonable  prices,  it  may  be 
considered  the  most  advantageous  for  the  individual  manufacturer. 

d.  Hydrated  Oxide  of  Iron. — This  class,  together  with  the  mine- 
ral coal  deposits,  constitutes  to  the  present  generation,  and  will  con- 
stitute, in  a  far  greater  degree,  to  future  generations,  a  solid  founda- 
tion of  wealth,  comfort,  and  happiness.  Upon  this  ore  the  citizens 
of  our  vast  Republic  may  safely  base  their  hopes  of  continual  pros- 
perity ;  its  sources  are  inexhaustible,  and  its  quality  of  such  a  na- 
ture, that  it  constantly  requires  the  mental  and  physical  exertions  of 
the  manufacturer  of  iron.  Improvements  in  arts  and  sciences  are  ap- 
plied with  advantage  to  this  branch  of  the  natural  deposits,  because 
the  material  varies  greatly  in  different  localities.  Constant  industry 
alone  will  enable  us  to  gain  the  advantage  over  difficulties  so  un- 
ceasing. But  this  ore  is  the  only  source  of  cheap  iron ;  and  by 
the  employment  of  charcoal,  it  yields  iron  even  of  good  quality. 

The  body  of  this  ore  may  be  divided  into  two  geological  classes; 
one  class  belongs  to  the  primitive  and  transition  rocks,  and  the  other 
to  the  tertiary  and  more  recent  deposits.  The  first  is  generally  of 
better  quality  than  the  second  ;  but  no  definite  rule  can  be  given  in 
relation  to  them.  Nearly  every  State  in  the  Union  is  abundantly 
supplied  with  this  kind  of  ore.  From  Maine  to  New  Jersey,  ore  of 
the  older  formations  abounds  ;  but  from  New  Jersey  to  Alabama, 
and  from  Western  New  York  and  Ohio  to  the  Mississippi,  within 
and  around  the  great  coal  formations,  the  great  class  of  the  hydrates, 
with  the  exception  of  the  compact  carbonates,  alone  is  to  be  found. 

On  the  working  of  this  ore  in  the  furnaces  and  forges,  we  shall 
speak  in  the  proper  place  ;  we  shall  confine  our  attention  at  present 
to  its  price.  It  is  generally  found  in  large  bodies  or  regular  veins, 
for  which  reason  the  working  or  raising  of  the  ore  is  cheap. 
Where  this  is  not  the  case,  it  is  best  not  to  commence  operations. 
If  an  amount  of  ore  sufficient  to  produce  a  ton  of  iron  exceeds  seven 
or  eight  dollars  at  the  furnace,  it  is  evident  that  competition  against 
those  works  which  pay  almost  nothing,  or,  as  in  Pennsylvania, 
Ohio,  Tennessee,  pay  but  from  one  to  one  dollar  and  a  half  per  ton 
for  iron,  would  be  unsafe.  Prosperous  times,  and  a  healthy  market, 
may  enable  us  to  endure  such  prices ;  but  when  the  reverse  is  the 
case,  a  business  cannot  safely  be  conducted.  Cheap  fuel  and  local 
facilities,  however  they  may  lessen  this  disadvantage,  are  not  suf- 
ficiently strong  to  overcome  a  difference  of  six  dollars  in  favor  of 


52  MANUFACTURE   OF   IRON. 

cheap  ore ;  and  it  is,  at  least  for  the  beginner,  doubtful  whether 
an  establishment  based  upon  expensive  ore  will  prosper.  Above 
all  things,  it  is  necessary  that  those  who  intend  to  start  on  a  new 
locality,  should  take  counsel  from  experienced  men  as  to  the  quality 
and  richness  of  the  ore ;  and  should  the  ore  happen  to  average  a 
given  quantity  of  iron,  and  should  the  price  of  an  amount  of  ore 
sufficient  to  yield  a  ton  of  iron,  be  but  six  dollars,  the  business 
may  be  attempted,  and  may,  with  industry  and  care,  be  successful. 
However  profitable  local  advantages  and  good  times  may  make  the 
iron  business,  to  those  who  find  themselves  surprised  by  a  sinking 
market  and  limited  means  the  losses  are  great.  Against  this  danger, 
good  quality  of  the  product  is  the  safest  guard ;  and  if  to  this  ad- 
vantage, that  of  cheap  ore  can  be  united,  most  difficulties  can  be 
successfully  met. 

e.  The  Compact  Carbonate — Argillaceous  Ore  of  the  Goal  Forma- 
toVw.-~-This  ore  is  very  abundant  in  the  large  western  coal  fields, 
and  will  be  a  source  of  iron  so  long  only  as  the  out-crops  of  this 
ore  which  are  oxidized,  and  hydrates,  can  be  wrought  at  reason- 
able prices ;  the  mining  of  this  kind  of  ore  cannot  be  considered  a 
safe  business,  for  the  raising  is  generally  very  expensive,  and  the 
roasting  and  smelting  difficult.  But  where  it  can  be  raised  at  one 
dollar  per  ton,  as  in  some  localities  on  the  Alleghany  River;  and 
where  the  quality  of  iron  is  of  no  consideration,  it  may  serve  as  a 
source  of  cheap  iron,  and  therefore  be  considered  valuable.  But 
we  must  warn  those  who  are  not  acquainted  with  the  working  of 
this  kind  of  ore,  that  they  will  generally  experience  difficulties  which 
are  very  apt  to  absorb  means  which,  to  enterprising  individuals,  are 
exhaustive.  We  shall  refer  to  this  subject  again  in  another  chapter. 

The  remaining  kinds  of  ore  are  of  so  small  amount  as  not  to  re- 
quire particular  attention.  Where  favorable  localities  offer  them- 
selves, an  enterprise  based  upon  such  ores  may  be  hazarded,  but 
with  due  consideration  of  price  and  market ;  for  iron  manufactured 
from  such  fancy  ores  is  generally  of  an  inferior  kind. 

XX.  Mining  of  Iron  Ore. 

The  mining  or  digging  of  iron  ore  does  not  differ  much  from  other 
mining  operations;  and  therefore  a  general  description  of  the  mining 
operation  might  suffice  in  this  particular  case.  However,  we  shall 
endeavor  to  present  a  clear  view  of  the  subject. 

Mining  is  an  art;  "it  is  a  highly  cultivated  mechanism,"  says 
Andrew  Ure,  Where  science  and  art  have  liberally  spent  their 


IRON   ORE.  53 

means,  architecture,  machinery,  and  plastic  arts  impart  instruction, 
through  the  medium  of  the  eye,  to  the  mind,  by  the  display  of  their 
respective  masterpieces.  But  this  is  not  the  case  in  the  art  of 
mining.  An  adequate  idea  of  the  high  cultivation  to  which  this 
branch  of  skill  and  industry  has  been  brought  cannot  be  exhibited 
at  one  view,  because  there  is  no  one  point  of  view  from  which  any 
other  art  can  be  completely  sketched.  The  subterraneous  structures 
present  some  of  the  most  interesting  monuments  of  the  genius  of 
the  human  mind.  Cultivated,  for  many  centuries,  under  the  guidance 
of  science  and  industry,  they  are  not,  and  cannot  be,  however 
great  and  ingenious,  the  objects  of  panoramic  representation.  The 
philosophical  mind  alone  can  contemplate  and  survey  them,  either 
in  whole  or  in  detail.  And  therefore  these  marvelous  regions,  in 
which  roads,  often  many  miles  long,  are  cut  and  highly  perfected, 
are  unknown  to  the  mass  of  the  people,  and  disregarded  by  men  of 
the  world.  When  chance,  curiosity,  or  interest  induces  such  to  de- 
scend into  these  dark  recesses  of  our  world,  they  merely  discover  a 
few  insulated  objects  which  make  a  vague,  indefinite  impression  on 
their  minds;  but  the  symmetrical  disposition  of  the  minerals,  and 
the  laws  which  govern  geological  phenomena,  which  serve  as  guides 
to  the  skillful  miners,  they  cannot  recognize.  From  exact  plans 
of  the  underground  workings  alone  can  a  knowledge  of  the  nature, 
extent,  and  distribution  of  the  useful  minerals  be  acquired. 

Among  the  great  variety  of  minerals,  apparently  infinite,  which 
compose  the  crust  of  the  earth,  science  has  demonstrated  the  pre- 
valence of  a  few  general  systems  of  rocks,  to  which  appropriate 
names  have  been  given.  The  more  recent  deposit,  or  loose  gravel 
and  earth,  is  called  alluvium;  the  more  ancient  deposit  of  this  kind, 
diluvium;  below  this  are  the  secondary  rocks;  the  next,  transition 
rocks;  and  the  oldest,  or  lowest  rocks,  primitive  formation,  or  primi- 
tive rocks.  Every  mineral  deposit  forms  more  or  less  of  a  plane, 
with  distinct  direction  and  inclination;  the  former  is  the  point  of 
azimuth  or  horizon  towards  which  it  dips,  as  north,  south,  south- 
west, &c.;  the  latter  is  the  angle  which  it  forms  with  the  horizon. 
The  direction  of  the  mineral  deposit  is  that  of  a  horizontal  line, 
drawn  in  its  plane.  Hence,  the  lines  of  direction  and  inclination 
are  at  right  angles  to  each  other. 

Masses  are  mineral  deposits  not  extensively  spread  in  the  form 
of  planes — mere  irregular  accumulations,  rounded,  or  spheroidal. 
Masses  generally  occur  in  the  primitive  rocks. 

Nests,  Concretions,  or  Nodules,  are  smaller  or  larger  masses  of 


54  MANUFACTURE   OF   IRON. 

minerals  found  in  stratified  rocks,  often  kidney-shaped,  tuberous, 
round,  or  spheroidal. 

Large  veins  are  called  lodes  ;  they  are  seldom  parallel  on  their 
opposite  surfaces,  and  sometimes  terminate  like  a  wedge;  their 
course  often  varies  from  that  of  the  strata  in  which  they  lie.  Lodes 
sometimes  pursue  for  a  distance  the  space  between  two  contiguous 
strata,  and  then  divide  into  several  branches.  Lodes  of  iron  ore 
are  found  in  almost  every  geological  formation. 

Veins  are  small  lodes,  which  often  traverse  the  strata  of  the  tran- 
sition rocks,  but  generally  run  parallel  in  the  coal  measures  and 
more  recent  formations. 

Iron  ore  is  met  with  in  all  the  different  geological  eras.  Among 
the  primitive  rocks,  we  find  magnetic  ore  and  specular  iron,  chiefly 
congregated  in  masses  or  beds,  sometimes  of  enormous  size;  as,  for 
instance,  the  magnetic  ore  on  Lake  Champlain.  In  transition 
rocks,  we  find  hematite  and  sparry  iron  ore,  generally  in  veins  or 
lodes;  seldom  in  masses.  In  the  coal  measures,  we  find  brown  iron 
ore  and  yellow  iron  ore  in  all  varieties,  globular  and  kidney-shaped 
oxide,  and  compact  carbonate,  generally  in  veins  of  greater  or  less 
extent.  Alluvial  and  diluvial  iron  ores  are  the  clay  ores,  granular 
ores,  bog  or  meadow  ore,  &c.  The  ores  which  belong  to  the  primi- 
tive period  always  have  a  metallic  aspect,  bright  lustre,  and  fur- 
nish the  richest  and  purest  iron.  The  ores  of  the  transition  rocks 
furnish  less  iron,  but  it  is  generally  of  the  most  profitable  kind. 
The  more  recent  the  age  of  ores,  the  poorer  they  are,  until,  be- 
coming more  and  more  earthy,  they  form  alluvial  soil. 

An  acquaintance  with  the  general  results,  collected  and  classified 
by  geology,  must  be  our  guide  in  investigations  of  mining.  This 
enables  the  observer  to  judge  whether  any  particular  district  con- 
tains iron  ore,  or  where  this  ore  can  be  found.  For  want  of  such 
knowledge,  many  persons  have  gone  blindly  into  researches  which 
were,  in  their  nature,  absurd  and  ruinous.  Geology  teaches  us  that 
in  primitive  rocks  no  stratified  veins  can  be  found;  neither  bog  ores, 
nor  fossil,  nor  calcareous  ores.  Transition  rocks  contain  veins  of 
hematite,  spathic  iron,  specular  iron,  &c.,  but  the  veins  run  either 
between  two  different  strata,  as  jura  lime  and  mica  slate,  or  tra- 
verse the  strata  at  indefinite  angles.  The  coal  measures  generally 
contain  iron  ore,  but  no  magnetic  ore,  spathic  iron,  specular  iron,  or 
brown  hematite.  We  must  be  satisfied  with  the  poorer  hydrates 
resulting  from  the  decomposition  of  the  compact  carbonates,  or 
the  decomposition  of  limestone  and  the  carbonates  themselves. 


IRON   ORE. 


55 


Alluvium  and  diluvium  furnish  only  bog  ores,  which  frequently  as- 
sume the  form  of  veins  and  masses  where  the  ferruginous  waters  de- 
scend upon  limestone  beds,  and  deposit  their  iron  upon  the  limestone. 
The  instruments  or  tools  for  mining  are  the  following :    The  pick, 


Fig.  7. 


Fig.  8. 


Miner's  pick. 


Miner's  mallet. 


Fig.  7,  made,  according  to  circumstances,  of  various  forms ;  but 
one  point  is  generally  edged,  and  the  other  pointed.  In  hard  mate- 
rial, as  sparry  ore,  or  compact  magnetic  ore,  the  edged  point  is 
of  no  use.  The  mallet.  Fig.  8,  is  used  for  driving  wedges,  and 
striking  the  hand-drill.  The  wedge.  Fig.  9,  is  driven  into  crevices  or 


Fig.  9. 


Wedge. 


Fig.  10. 


Sledge. 


small  openings,  made  with  the  pick,  to  detach  pieces  from  the 
rock  or  mine.  The  sledge,  Fig.  10,  is  a  mallet  of  from  five  to  six 
pounds  weight,  and  is  used  to  break  larger  pieces  of  rock  or  mine. 

Fig.  11. 


Miner's  shovel. 


Fig.  11  represents  a  miner's  shovel,  which  is  pointed,  so  as  to  pene- 
trate the  coarse  and  hard  fragments  of  minerals  and  rocks.   All  these 
tools  should  be  well  steeled  and  tempered,  and  kept  in  good  repair. 
Besides  these,  the  miner  requires  the  following  blasting  tools : 


Fig.  12. 


Fig.  13. 


Hand-drill. 


Tamping-bar. 


56  MANUFACTURE   OF   IRON. 

A  hand-drill,  Fig.  12,  which  is  a  bar  of  iron  or  steel,  edged  at 
one  end,  and  headed  at  the  other — both  well  hardened  and  tem- 
pered ;  the  scraper,  a  small  iron  rod,  with  a  square  hook  on  one 
end,  to  take  the  boremeal  out  of  the  hole ;  and  a  copper  needle, 
which  is  a  simple  wire,  one-fourth  of  an  inch  thick,  somewhat 
tapered  at  one  end.  Many  miners  are  in  the  habit  of  using  iron 
needles,  but  these  are  very  dangerous,  and  should  not  be  employed; 
even  limestone  rock  is  no  security  against  accidents  from  self-dis- 
charges. The  tamping-bar,  Fig.  13,  is  a  bar  of  round  iron,  with  a 
groove  to  fit  the  needle. 

A  few  remarks  in  relation  to  blasting  may  be  as  appropriately 
made  here  as  in  any  other  place.  If  there  is  any  class  of  human 
beings  regardless  of  their  lives,  the  miners  are  that  class.  This 
remark  applies  particularly  to  blasting.  Foremen,  and  conductors 
of  mining  operations,  should  be  very  careful  and  determined  in  their 
general  orders,  for  the  workmen  will  disregard  the  rules  and  regu- 
lations adopted  for  mutual  safety,  and  bring  themselves,  and  fre- 
quently their  fellow-workmen,  in  danger  of  life  and  limb.  Of  all 
the  blasting  tools,  the  iron  needle  is  the  most  dangerous,  and  oc- 
casions more  loss  of  life  than  anything  else  in  the  subterranean 
cavities.  Iron  needles  are  very  apt  to  fire  the  powder,  notwithstand- 
ing the  greatest  care,  and  should  not  be  used  in  any  quarry  or 
mine.  The  copper  needle  is  perfectly  safe.  An  iron  tamping-bar 
has  occasionally  caused  premature  discharges,  but  may  be  safely 
used  in  limestone  and  iron  ore.  To  avoid  the  dangers  arising  from 
an  iron  tamping-bar,  the  face  is  frequently  made  of  hard  copper.  In 
stone  quarries,  where  deep  and  vertical  holes  can  be  drilled,  the 
needle  and  tamping-bar  may  be  dispensed  with,  and  the  hole  filled 
with  dry,  coarse  sand.  This  mode  of  blasting  consumes  rather 
more  powder,  but  is  without  danger.  In  mines  where  no  deep, 
and  very  seldom  vertical,  holes  are  available,  the  needle  and  ram- 
rod cannot  be  dispensed  with;  this  increases  the  necessity  that  these 
instruments  should  be  of  the  most  perfect  kind. 

The  mining  operation  may  be  divided  into  two  branches:  to  wit, 
exploring  and  mining.  The  first  requires  scientific  knowledge ; 
the  latter,  experience.  After  a  general  survey  of  the  geological 
position  is  taken,  and  the  situation  of  an  iron  ore  or  coal  vein  ascer- 
tained, trenches  may  be  opened ;  if  the  searches  are  made  on  a  steep 
hillside,  the  loose  ground  is  to  be  removed,  and  the  digging  continued 
until  the  solid  strata  of  rock  are  laid  open.  In  case  we  do  not  find 
the  expected  vein,  the  trench  may  be  continued  either  up  hill  or 


IRON  ORE.  57 

down  until  the  mineral  or  coal  vein  is  found.  In  this  mode  of  ex- 
ploring, it  is  always  best  to  select  the  steepest  places,  because  there 
the  least  covering  is  to  be  expected,  and  to  commence  the  work- 
ings always  below  the  supposed  vein  :  for  the  mineral  will  naturally 
sink  down  the  hill,  and  fragments  will  serve  as  guides.  Where 
the  fragments,  called  blossoms  of  the  vein,  cease,  we  may  safely 
rely  upon  being  near  the  vein.  This  way  of  exploring  is  very 
expeditious  and  effectual,  but  only  applicable  in  stratified  rocks, 
where  the  situation  of  the  vein  can  be  previously  ascertained. 
Where  the  exploring  by  trenches  or  ditches  cannot  be  effected, 
because  there  is  too  much  loose  ground,  or  alluvium,  covering 
the  strata,  we  proceed  to  sink  a  shaft  in  the  most  favorable  place. 
Where  the  vein  is  so  low  that  but  a  few  feet  of  the  roof  rock  may 
be  penetrated,  this  rock  will  secure  the  bottom  of  the  shaft  in 
case  a  thorough  investigation  of  the  mineral  vein  is  contemplated. 
Fig.  14  is  a  section  of  such  a  shaft :  a,  the  mineral  vein :  6,  the 

Fig.  14. 


Sinking  a  shaft. 

overlaying  rock;  <?,  alluvium  or  gravel.  Such  a  shaft  is  'com- 
monly four  feet  wide,  or,  to  save  expense,  as  narrow  as  possible;  and 
if  the  ground  or  gravel  is  not  very  loose,  no  timbering  should  be 
done  until  the  vein  is  found,  and  the  progress  of  the  work  deter- 
mined upon. 

The  cost  of  sinking  such  shafts  varies,  according  to  circum- 
stances, from  one  dollar  to  three  dollars  per  foot,  should  the  depth 
not  be  greater  than  from  thirty  to  seventy  feet.  Beyond  the  depth 
of  seventy  feet,  and  beyond  the  loose  ground,  which  requires  tim- 


58  MANUFACTURE   OF   IRON. 

bering,  the  cost  augments  considerably.  If  hillsides  are  covered 
with  alluvium  of  the  thickness  of  only  six  or  twelve  feet,  and  the 
location  of  the  mineral  vein  not  exactly  known  previous  to  actual 
search,  pits  or  shafts  may  be  sunk  one  above  the  other,  so  long  as 
fragments  of  the  vein  in  question  appear  in  the  bottom  of  the  shaft; 
and  if  the  blossoms  disappear,  the  last  pit  is  dug  until  the  vein  is 
struck  upon.  If  mineral  masses,  or  veins,  are  so  far  below  the  sur- 
face, that  it  is  doubtful  whether  the  sinking  of  a  shaft  may  be  suc- 
cessfully effected,  boring  may  be  resorted  to.  Should  it  be  ascer- 
tained that  a  mineral  bed  is  so  situated  that  a  perpendicular  hole 
may  be  reasonably  expected  to  reach  it,  a  small  hole  from  two  to  two 
and  a  half  inches  in  diameter  may  be  driven  down  upon  the  mate- 
rial searched  for.  The  boring  of  such  a  hole  of  three  hundred  feet 
in  depth  seldom  exceeds  one  dollar  per  foot ;  from  this  depth  to 
that  of  five  hundred  feet,  about  two  dollars,.  The  manipulations 
required  are  simply  those  employed  in  boring  Artesian  wells ;  and 
we  shall  give  a  short  description  of  this  interesting  mode  of  pene- 
trating the  crust  of  the  earth. 

A  brief  description  of  the  method  of  boring  salt  wells  on  the 
Ohio  River,  and  its  branches,  will  answer  every  purpose;  but 
those  who  intend  to  engage  in  the  experiment  should  employ  men 
who,  besides  being  well  acquainted  with  the  business,  are  able  to 
conduct  it  safely  and  advantageously.  When  a  place,  where  the 
rock  is  to  be  penetrated,  is  selected,  a  hole  like  the  shaft  of  a  well 
is  dug  down  to  the  solid  rock  ;  in  the  centre  of  this  shaft  is  a  wooden 
log,  set  perpendicularly,  its  base  well  fitted  to  the  rock.  A  trunk  of 
red  oak,  or  other  hard,  sound  wood,  and  sufficiently  long  to  reach 
above  the  ground,  is  generally  employed.  This  log  is  properly  fast- 
ened and  buried,  so  that,  when  the  shaft  is  filled  up  again,  a  foot  or 
less  of  the  trunk  projects  above  ground.  Over  this  a  wooden  frame- 
work tower,  from  twenty-five  to  thirty  feet  high,  formed  of  scantlings 
from  six  to  seven  inches  square,  is  erected.  On  the  top  of  this  tower, 
a  pulley  is  fastened,  over  which  a  two  inch  hemp  rope  may  be  laid; 
the  one  side  of  the  periphery  of  this  pulley  forms  the  centre  of  the 
bore  hole,  and  a  plumb-lead,  let  down  from  it,  ought  to  hit  the  cen- 
tre of  the  buried  log.  From  this  centre,  a  perpendicular  hole,  of 
the  size  of  the  intended  bore  hole,  is  bored  with  an  auger,  through 
the  wood,  down  to  the  rock.  This  wood-block  secures  the  mouth 
of  the  well.  The  boring,  or  penetrating  of  the  rock  is  done  in  an 
improved  Chinese  manner,  by  means  of  a  hemp  rope  of  two  inches  in 
diameter,  and  a  wrought  or  cast  iron  drill  of  from  two  to  five  hundred 


Vi 


IRON  ORE.  59 

pounds  weight :  the  motion  to  the  drill  is  given  by  a  small  steam- 
engine.  This  arrangement  is  a  very  good  one,  for  it  penetrates 
the  earth  rapidly,  and  by  it  the  expense  of  a  two  and  a  half  inch 
hole  very  seldom  exceeds  one  dollar  or  one  dollar  and  fifty  cents 
per  foot  to  a  depth  of  three  hundred  feet.  The  old  German  method 
of  sinking  small  holes  by  means  of  square  iron  rods,  which  is  at 
present  mostly  employed  in  Europe,  is  very  expensive,  slow,  and 
uncertain.  Another  method,  tried  in  Germany,  of  boring  by  means 
of  flat  iron,  strong  hoop  iron,  is  very  ingenious,  and  possibly  might 
rival  the  American  or  improved  Chinese  mode,  if  prosecuted  with 
vigor  and  intelligence. 

When  the  location,  thickness,  and  quality  of  the  mineral  in  ques- 
tion are,  by  means  of  the  boring,  duly  determined,  the  following 
working  plan  may  be  adopted :  Either  to  sink  a  shaft  in  the  direc- 
tion of  the  bore  hole ;  or,  where  the  mineral  is  sufficiently  high,  and 
above  high  water  mark  of  the  neighboring  river,  to  drive  a  level,  or 
horizontal  gallery  from  a  convenient  place  on  the  base  of  the  hill, 
and  reach  in  that  way  the  ore  or  coal  bed.  The  manner  of  doing 
this  is  generally  determined  by  a  consideration  of  expenses,  in  which 
that  of  raising  the  material  is  the  most  important  element. 

Mining,  specifically  considered,  includes  two  distinct  operations : 
to  wit,  excavation,  and  subterranean  work.  Excavation,  i.  e.  work- 
ings in  the  open  air,  presents  few  difficulties,  and  occasions  little  ex- 
pense. This  method  is,  at  present,  generally  practiced  in  the  United 
States  for  digging  iron  ore,  and  will  not,  for  some  time  to  come, 
be  superseded  by  any  other  method ;  for  there  are  immense  deposits 
of  ore  which  can  be  reached  in  this  way,  and  present  of  course  greater 
advantages  than  underground  workings.  Workings  in  the  open  air 
are  generally  preferred  where  the  deposits  are  close  to  the  surface. 
In  fact,  no  other  method  can  be  resorted  to  in  this  case,  if  the  sub- 
stance to  be  raised  is  covered  with  incoherent  matter.  The  follow- 
ing rules  must  be  observed :  Conduct  the  workings  in  regular  ter- 
races, so  as  to  facilitate  the  cutting  down  of  the  earth,  and  the  removal 
of  the  mine  and  rubbish  with  the  least  possible  expense.  Guard 
against  the  crumbling  clown  of  the  sides,  by  giving  them  proper  slope, 
or  by  props  and  timber.  Ditches,  or  water  drains,  must  be  dug,  so 
as  to  keep  the  workings  dry,  and  prevent  disturbance  in  wet  seasons. 
Open  workings  are  resorted  to  in  quarrying  limestone,  digging  fire- 
clay, bog  ores,  the  out-crop  of  the  argillaceous  ores  of  the  coal  for- 
mation, and  various  other  ores ;  as  well  as  in  digging  turf  and 
brown  coal,  and  most  of  the  anthracite  of  Pennsylvania.  The  main 


60  MANUFACTURE   OF   IRON. 

object  to  be  considered  in  open  workings,  or  strippings,  is,  to  re- 
move heavy  masses  of  earth  with  the  least  possible  expense.  This 
can  be  done,  if  such  arrangements  have  been  made  that  the  rub- 
bish need  not  be  carried  too  far,  or  too  high,  and  no  shovelful  of 
ear.th  thrown  twice.  As  a  general  rule,  it  may  be  said,  that,  under 
common  circumstances,  one  foot  of  stripping  can  be  done  for  every 
inch  of  iron  ore,  without  going  to  excessive  or  high  wages. 

Subterranean  workings  include  two  distinct  operations :  to  wit, 
preparatory  or  dead  workings,  and  those  of  extraction.  The  pre- 
paratory workings  consist  of  those  excavations  which  do  not  pay  their 
expenses  in  the  material  raised  ;  and  if  the  value  of  the  ore  or  coal 
yielded  from  them  is  little  or  nothing,  the  miners  call  such  work- 
ings "dead  work."  They  also  consist  in  constructing  drifts  or 
levels,  or  pits  and  galleries,  for  the  purpose  of  conducting  the  miner 
to  the  point  most  proper  for  attacking  the  deposit  of  ore,  or  for  trac- 
ing the  extent  of  the  mineral;  as  well  as  in  arranging  plans  for  the 
circulation  of  air,  the  discharge  of  waters,  and  the  transport  of  the 
extracted  minerals.  The  preparatory  works  in  mining  are  often 
very  considerable,  and  demand,  in  many  instances,  great  attention. 
Where  ore  or  coal  veins  are  small,  and  the  operations  require  exten- 
sion over  a  large  field,  these  works  frequently  absorb  more  means 
than  contemplated,  and  are  not  seldom  the  ruin  of  otherwise  well 
calculated  enterprises.  The  exploring  of  small  or  irregular  running 
ore  veins,  which  are  common  in  the  coal  measures,  occasions  great 
expense.  Iron  works  based  upon  such  deposits,  should  be  com- 
menced on  a  small  scale,  and  a  certain  amount  of  capital  should 
be  invested  in  exploring  expenses,  before  improvements  of  a  more 
permanent  character  are  made.  The  ore  deposits  of  the  coal  for- 
mation, in  the  Western  States,  are  often  very  deceptive.  In  a  com- 
paratively small  compass,  they  exhibit  different  kinds  of  ore  ;  these 
either  belong  to  insignificant  bodies  of  ore  imbedded  in  shale,  or  are 
the  out-crops  of  the  blue  carbonates,  or  precipitates  upon  limestone 
beds,  which  are  never  of  great  extent.  In  all  such  cases,  the  enter- 
prising owner  of  iron  works  based  upon  such  deposits  is  in  a  difficult 
situation,  for  the  price  of  his  ore  generally  exceeds  his  modest  cal- 
culations; the  dead  works  absorb  more  means  than  he  expected;  and 
the  frequent  change  of  the  ore  occasions  disturbances  in  the  smelt- 
ing operations,  injurious  to  the  quality  and  price  of  the  manufac- 
ture. In  such  cases,  where  small  or  unexplored  ore  deposits  are 
to  be  used,  it  is  the  most  advisable  plan  to  follow  the  out-crops  ;  to 
go  with  great  caution  to  underground  work;  to  make  it  a  rule  not  to 


IRON    ORE. 


61 


speculate  upon  the  improvement  of  the  ore  vein ;  and  to  drift  only 
on  those  places  where  the  quality  and  quantity  of  the  ore  are  per- 
fectly known,  and  where  the  operating  miner  offers  fair  prices,  with- 
out extra  pay,  for  dead  work.  Such  small  mineral  deposits  have, 
besides,  the  disadvantage  of  expensive  dead  work,  and  generally 
occasion  greater  expense  for  superintendence,  as  well  as  greater 
expense  for  making  and  repairing  roads. 

When  a  mineral  vein  is  explored,  and  we  have  determined  to 
proceed  to  drifting,  the  first  point  we  are  required  to  settle  is  the 
lowest  situation  of  the  vein.  If  the  hauling  of  the  mineral  cannot 
be  effected  from  such  a  point,  it  is  necessary  to  drain  the  waters, 
and  afford  the  workmen  dry  rooms.  Such  points  are  found  either 
by  exploring  the  out-crop  on  opposite  slopes  of  a  hill,  or  by  open- 
ing at  that  side  of  a  hill  whence  the  strongest  springs  issue.  Where 
iron  ore  is  deposited  on  limestone,  draining  may  be  safely  effected, 
if  we  open  a  drift  in  the  strongest  spring  which  can  be  found  within 
our  possessions.  When  the  plan  and  place  are  fixed,  the  miners 
dig  an  opening  six  feet  in  height,  and  four  feet  wide,  taking  care 

Fig.  15. 


Timbering  of  a  drift. 

that  its  floor  shall  be  below  the  bottom  part  of  the  mineral,  and 
formed  of  solid  ground  or  hard  rock.  The  open  ditch,  thus  com- 
menced, is  not  continued  very  far  before  the  miners  begin  to  timber 
their  drift.  This  can  be  done  at  the  very  starting-point.  Its  ob- 
ject is,  to  prevent  the  slipping  in  of  the  earth,  and  to  prevent,  in 


62 


MANUFACTURE   OF   IRON. 


•winter,  the  filling  of  the  open  drift  with  snow.  Both  of  these  acci- 
dents give  much  trouble  to  miners.  The  timbering  is  done  by  the 
miners  themselves  ;  and  a  good  miner  performs  this  work  properly  ; 
that  is,  he  sets  his  posts  in  a  straight  line,  and  fastens  his  caps  in 
such  a  way  that  a  crushing  of  the  timber  neither  from  above  nor 
from  the  sides  is  possible.  The  general  way  of  timbering  a  drift  is 
represented  in  Figs.  15  and  16  :  a,  a,  a,  a,  a  represent  posts,  gene- 
Fig.  16. 


Timbering  of  a  drift. 

rally  six  or  six  and  a  half  feet  long,  somewhat  slanted  in  the  view, 
so  as  better  to  resist  the  side  pressure.  The  caps  5,  6,  b,  b  are  split 
timbers  of  ten  or  twelve  inches  in  diamater,  five  feet  long,  and  on 
each  end  is  a  shoulder  in  which  the  posts  fit.  The  posts  must  rest 
on  solid  rock  when  possible,  to  prevent  their  sinking,  d  represents 
a  water-drain  covered  with  planks ;  and  e,  e  the  rails  of  a  train-road, 
made  of  sawn  timbers,  planks,  or  iron  rails,  or  of  flat  bar  iron  spiked 
upon  timber.  /,  /,  /,  /,  &c.,  are  split  timbers  from  two  to  three 
inches  thick,  which  cover  the  caps  and  posts,  to  prevent  the  dropping 
in  of  the  gravel  and  stones.  The  frames,  consisting  of  two  posts 
and  one  cap,  are  generally  one  yard  distant  from  each  other.  .That 
part  of  the  structure  which  is  outside  of  the  hill,  is  to  be  covered 
with  earth  to  keep  the  drift  warm  in  winter,  cold  in  summer,  and 
prevent  the  decay  of  the  timber. 


IRON  ORE.  63 

Coal  and  iron  ore  are  minerals  which  cannot  bear  expensive  pre- 
paratory works.  We  shall  confine  our  remarks  to  the  most  simple 
forms  of  mining  operations,  for  a  thorough  description  of  exten- 
sive mines  is  not  necessary.  Drifts  and  shafts,  constructed  in  the 
cheapest  possible  way,  are  the  only  allowable  means  of  excava- 
tion, and  to  these  plans  we  shall  confine  our  attention.  If  an  ore 
or  coal  deposit  cannot  be  reached  by  drifting — either  because  the 
deposit  is  under  the  general  water  level,  or  because  the  extent  of 
our  property  does  not  permit  us  to  reach  the  lowest  point  of  the  de- 
posit— we  are  forced  to  work  by  shafts,  and  hoist  minerals  and  rub- 
bish, as  well  as  the  waters,  by  machinery.  The  present  state  of  the 
mining  operations  of  the  United  States,  the  extensive  out-crops,  and 
the  abundance  of  minerals  above  the  water  levels,  make  the  use 
of  shafts  somewhat  expensive  in  the  first  outlay;  and  as  capital 
cannot  yet  be  advantageously  employed  against  industry,  it  will 
take  a  long  time  before  a  general  system  of  cultivated  mining 
operations  can  be  expected.  Shafts  are  simply  vertical  excavations 
sunk  to  the  mineral  vein  (Fig.  14);  but  a  work  shaft  is  larger 
than  an  exploring  shaft,  often  exceeding  ten  feet  square.  Their 
dimensions  depend  entirely  on  the  amount  of  matter  to  be  raised. 
Coal  shafts  are  generally  large,  so  as  to  permit  the  ascent  and  de- 
scent of  a  kibel  or  wagon  at  the  same  time;  while  ore  shafts  are 
sufficiently  large  if  they  permit  the  passage  of  a  box  which  will 
contain  from  five  to  seven  hundred  pounds  of  ore.  The  timbering  of 
shafts,  as  well  as  that  of  drifts,  varies  inform,  according  to  the  nature 
and  locality  of  the  ground  which  they  penetrate,  and  the  purposes 
which  they  are  meant  to  serve.  The  shafts  to  be  secured  by  timber 
are  either  square  or  rectangular;  this  form,  besides  being  more  con- 
venient for  the  miner,  renders  the  application  of  timber  more  easy. 
The  wood  work  consists  generally  of  frames,  the  spars  of  which  are 
from  six  to  ten  inches  square,  and  placed  from  two  to  three  feet 
apart;  seldom,  except  in  very  soft  ground,  placed  more  closely. 
Whether  the  shaft  is  vertical  or  inclined,  the  frames  are  always 
placed  so  as  to  stand  perpendicular  upon  its  basis  or  axis.  The 
mining  operations,  which  extend  from  the  lowest  point  where  the 
shaft  reaches  and  sinks  through  the  mineral,  are  not  in  the  least 
different  from  those  pursued  in  drifts,  and  will  be  included  in  the 
general  explanations.  Waters,  if  not  extracted  by  a  separate  drain, 
must  be  hoisted,  either  in  large  buckets,  if  the  amount  is  small, 
or,  if  large,  with  pumps. 

It  is  of  considerable  importance  what  kind  of  timber  is  used  in 


64  MANUFACTURE   OF  IRON. 

mines.  In  ore  mines,  locust,  white  oak,  and  red  oak  are  preferable; 
but  in  coal  mines,  pitchy  pine  is  the  most  durable.  Unless  other- 
wise stated  in  the  contract,  it  is  generally  understood  that  miners 
put  the  timber  in  themselves.  But  the  timber  is  to  be  delivered  at 
the  mine,  or  at  the  mouth  of  the  pit,  ready  split,  and  cut  into  proper 
lengths. 

The  cost  of  drifting  varies  according  to  the  matter  to  be  pene- 
trated. In  slaty  rock,  primitive  slate,  secondary  slate,  shale,  &c., 
a  drift  six  feet  in  height,  and  four  and  a  half  feet  at  the  base, 
costs  three  dollars  a  yard  running  measure;  tools  and  gunpowder 
found.  If  ore  or  coal  is  met  with,  nothing  extra  is  paid  for  it.  It 
belongs  to  the  owner,  and  should  be  put  aside.  Drifts  in  primitive 
and  transition  rocks  will  cost  from  five  to  fifteen  dollars  a  yard,  if 
tolerably  wide.  These  rocks  do  not  require  timber,  and  to  that 
extent  save  mining  expenses.  Limestones  are  not  easily  pene- 
trated; they  cost  from  five  to  ten  dollars  a  yard;  require,  oftentimes, 
strong  timbers,  and  are  not  very  safe.  Drifts  may  be  put  into  coal 
veins  at  from  two  to  three  dollars,  according  to  roof  and  floor;  strong 
roof  and  hard  floor  make  the  cheapest  and  best  drifts.  The  sink- 
ing of  shafts  is  expensive.  Hard  primitive  and  transition  rock 
averages  from  fifteen  to  thirty  cents  a  cubic  foot;  and,  in  the  coal 
formations,  from  ten  to  twelve  cents,  besides  timbering  and  timber. 
In  coal  formation  and  limestone,  shafts  are  frequently  very  expensive, 
on  account  of  the  water  which,  accumulating  in  the  bottom,  dis- 
turbs the  works  going  on.  When  such  troubles  happen,  and  the 
pumps  employed  are  not  strong  enough  to  hold  the  water,  strong 
frames,  and  waterproof  planking,  should  be  placed  so  as  to  keep  the 
fissures  closed. 

Besides  the  expense  of  drifting,  and  that  of  dead  levels  through 
the  mineral,  air  shafts  in  deep  workings  occasion  great  expense 
both  of  money  and  of  time.  They  are  indispensable  where  bad  air 
troubles  the  diggers,  and  are  needed  in  coal  pits  to  prevent  explo- 
sions, which  are  often  ruinous  both  to  the  men  and  to  the  works. 
Davy's  safety-lamp  is  but  an  imperfect  prevention,  and  should  not 
be  depended  upon.  Good  air  shafts  can  be  erected  everywhere;  and 
that  economy  is  misapplied  which  seeks  to  dispense  with  them. 
Fresh  air,  besides  the  advantage  it  affords  of  greater  security  to  the 
lives  of  the  workmen,  preserves  the  timbering  of  the  mines  better 
than  anything  else. 

If  an  ore  vein  is  both  regular  and  of  great  extent,  a  gallery  or 
level  may  be  driven  into  it  far  enough  to  permit  the  construction  of 


IRON  ORE. 


65 


a  number  of  chambers  or  rooms,  for  the  miners.  Where  the  vein  is 
thin,  say  from  ten  to  fifteen  inches,  let  us  assume  that  one  miner  is 
able  to  dig  on  an  average  one  ton  of  ore  in  twelve  hours :  If  fifty 
tons  are  needed  in  twenty-four  hours,  and  if  the  mining  is  carried 
on  in  the  day-time  alone,  twenty-five  rooms  are  required;  but  if 
carried  on  both  day  and  night,  half  that  number  is  sufficient.  One 
room  is  seldom  smaller  than  five  or  six  yards,  and,  if  the  roof  is 
solid  and  strong,  sometimes  from  twenty  to  thirty  yards  wide. 
Two  miners  generally  occupy  one  room.  If  this  calculation  is 
correct,  and  rooms  of  fifteen  yards,  with  five  yard  pillars,  adopted, 

20     25 
it  will  require  a  drift  of  - — '- -250  yards  long  to  deliver  a  safe 

and  regular  supply  of  fifty  tons  of  ore  a-day.  Here  we  may 
economize  in  dead  work,  but  if  done,  it  is  on  account  of  regularity 
and  order.  Fig.  17  is  a  plan  of  such  a  mine.  The  main  drift 


Ground-plan  of  the  interior  of  a  mine. 

fl,  a  may  be  in  the  lowest  axis  or  centre  of  the  vein,  and  the  waters 
from  all  the  rooms  5,  5,  5,  &c.  can  be  conducted,  by  means  of  the 
branches  c,  <?,  to  the  main  drift ;  but  where  this  is  not  the  case, 
5 


66 


MANUFACTURE   OF  IRON. 


the  branches  slionld  be  slanted  towards  the  mouth,  with  due  regard  to 
the  free  discharge  of  the  waters.  The  latter  arrangement  generally 
has  the  disadvantage  of  limiting  rooms  to  one  side  of  the  branches, 
and  not  unfrequently  of  limiting  branches  to  one  side  of  the  main 
drift.  This  circumstance,  of  course,  increases  the  expense  of  dead 
work.  If  rooms,  in  this  way  of  working,  are  exhausted,  and  no 
extension  of  the  branches  contemplated,  the  pillars  may  be  taken 
out  by  commencing  at  the  farthest  end  (which  can  be  done  with 
perfect  safety,  if  the  roof  is  strong),  and  the  rubbish  piled  so  as 
to  support  the  sinking  roof*  In  case  any  extension  of  branches 
or  main  drift  is  projected,  it  is  better  to  leave  the  pillars  standing 
until  a  final  abandonment  of  the  mine  is  in  view.  A  good  roof 
will,  in  this  way,  permit  the  taking  out  of  every  ton  of  ore. 

If  a  thin  vein  of  ore  is  overlaid  by  shale,  which,  brittle  in  its 
stature,  cannot  long  resist  the  pressure  from  above,  a  different  plan 
of  mining  is  to  be  pursued.  As  a  cheap  work,  this  plan  well  suits 
the  tendencies  of  this  country.  The  miner  opens  a  drift  in  the  com- 
mon way;  he  is  not  very  careful  in  timbering  it,  giving  it  but  suffi- 
cient strength  to  serve  his  purposes ;  he  drives  his  level  with  the 

Fig.  18. 


Drifting  of  ore. 


IRON  ORE.  67 

greatest  possible  advantage  and  speed,  as  far  as*  he  sees  fit — twenty 
yards  or  one  hundred  yards ;  and,  when  he  thinks  this  level  is 
pushed  far  enough  in,  he  opens  rooms  on  both  sides  of  his  drift, 
and  piles  rubbish  and  stones  against  the  timber  of  the  drift,  to  se- 
cure the  roof  in  case  the  timber  gives  way.  He  continues  to  take 
out  the  ore  on  both  sides  of  the  drift,  as  far  as  he  with  safety 
can  venture,  and  then  recedes  towards  its  mouth.  When  this  is 
reached,  there  is  no  further  use  of  the  mine,  for,  if  not  behind 
him,  the  roof  will  be  down  shortly  after  he  leaves.  Fig.  18  repre- 
sents the  plan  of  such  a  drift :  a,  a  is  the  original  drift;  5,  b,  excava- 
tions or  rooms ;  c,  c,  c,  <?,  timbers,  against  which  he  piles  the  rubbish 
taken  from  5,  5,  leaving  only  an  opening  where  he  is  working,  to 
carry  out  his  ore.  This  plan  of  working  is  a  cheap  one,  and  answers 
well  where  an  extensive  out-crop  of  ore  is  at  our  disposal;  or  where 
the  out-crop  is  the  only  valuable  ore,  which  is  the  case  with  most 
of  the  argillaceous  ores  of  the  coal  formation ;  or  where  iron  ores 
are  deposited  on  limestone,  and  do  not  extend  into  the  interior. 

These  two  are  the  most  common  plans  of  working  iron  ores,  and 
answer  every  purpose  where  the  veins  can  be  made  accessible  by 
an  out-crop  of  low  situation ;  but  where  the  out-crop  is  high — 
that  is,  where  the  interior  is  lower  than  the  out-crop — a  more 
expensive  plan  must  be  adopted,  either  by  shafts,  when  these  are 
the  cheaper  method,  or  by  a  dead  level,  to  be  driven  towards  the 
lowest  point  of  the  deposit. 

Upon  the  working  of  coal  mines  we  shall  treat  in  the  next  chapter, 
as  this  subject  is  connected  with  that  of  fuel,  and  differs  in  many 
respects  from  the  mining  of  ore ;  still,  in  both  cases,  the  utmost 
economy  is  needed,  as  each  presents  a  great  field  for  spending 
money,  and  as  operations,  once  commenced,  cannot  be  abandoned 
without  losses.  But  where  these  operations  are  of  a  doubtful  nature, 
the  continuance  of  our  business  only  involves  an  increase  of  the 
loss.  Above  all  things,  a  careful  geological  survey,  and  local  ex- 
plorations, should  precede  every  mining  enterprise. 

Wages  for  digging  iron  ore  vary,  of  course,  considerably,  accord- 
ing to  location  and  facilities;  a  one  foot  vein  of  magnetic  ore,  specu- 
lar ore,  and  sparry  iron,  may  be  wrought  at  two  dollars  a  ton,  if  the 
undermining  is  not  too  hard,  that  is,  if  the  rock  below  the  ore  is  soft 
enough  to  be  easily  cut  by  a  sharp  pickaxe;  sometimes  even  at  one 
dollar,  if  the  bed  is  heavy,  and  if  the  ores  belong  to  the  crystallized 
kind.  Hydrates,  such  as  shell  ores,  brown  iron  stone,  and  yellow 
hydrate,  can  be  dug  at  one  dollar  a  ton,  and,  in  strippings  and  thick 


68  MANUFACTURE   OF  IRON. 

veins,  at  a  still  less  cost.  The  compact  carbonates  of  the  coal 
measures  are  the  most  expensive,  very  seldom  less  than  two  dollars 
a  ton  ;  they  average  three,  and  frequently  even  four  dollars  a  ton : 
tools  and  gunpowder  to  be  charged  to  the  miners.  To  this  item 
are  to  be  added,  the  expense  of  hauling,  repair  of  roads,  ore  leave, 
timber,  dead  work,  and  interest  on  the  capital,  which,  in  many 
cases,  will  add  twenty-five,  and,  in  some  cases,  fifty  cents  to  the  ori- 
ginal cost.  Ore  leave  requires  attentive  consideration,  where  the 
ores  are  poor  and  other  expenses  high.  In  some  instances,  it  is  be- 
yond the  power  of  an  owner  of  iron  works  to  buy  all  the  ore  lands  re- 
quired for  the  prosecution  of  his  business,  and  he  is  compelled  either 
to  pay  an  ore  rent,  or  buy  the  ores ;  both  cases  require  caution, 
however  simple  the  business  appears  to  be.  The  main  difficulties  are 
a  strike  for  higher  prices,  and  a  consequent  disturbance  in  the 
operations,  daily  attempts  to  adulterate  the  ores,  and  cash  payments. 
Still  there  may  be  cases  where  ore  grants  and  buying  of  ore  are 
preferable  to  the  purchase  of  ore  lands ;  as,  for  instance,  where  it  is 
impossible  to  ascertain  the  extent  of  ore,  or  where  the  price 
appears  to  be  high,  or  where  there  is  lack  of  judgment  on  the  part 
of  the  buyer,  or  want  of  means,  or  doubtful  times  and  market. 

XXI.  Fluxes. 

Any  substance  which  promotes  the  melting  of  another  is  called  a 
flux.  The  term  is  especially  applied  to  those  materials  which  pro- 
mote the  melting  of  earths,  and  the  separation  of  the  metals  from 
their  oxides.  Of  this  latter  class  it  is  our  intention  at  present  to 
speak. 

Fluxes  are  most  important  matters  to  the  metallurgist ;  they  test 
the  intellect  of  the  iron  master,  and  are  the  science  of  his  whole 
business.  We  shall  speak  of  the  theory  of  fluxes  in  a  future  chap- 
ter, and  at  present  confine  our  attention  simply  to  a  description 
of  the  materials  used  as  fluxes,  and  their  raising,  as  far  as  their 
application  to  the  blast  furnace  is  concerned.  Fluxes,  in  practical 
use  in  the  blast  furnace,  are  lime,  magnesia,  clay,  silex,  and  the 
foreign  matter  in  the  fuel. 

a.  Lime. — It  is  hardly  necessary  to  give  a  mineralogical  descrip- 
tion of  lime,  nor,  for  our  purpose,  would  this  description  be  of  much 
use.  Almost  everybody  knows  how  to  distinguish  limestones  from 
other  stones.  Limestones  are  generally  applied  in  the  blast  furnace 
instead  of  burnt  lime,  though  a  weaker  alkali ;  the  stone  is  prefer- 
able, for  reasons  we  intend  to  explain  in  another  chapter.  Pure 


IRON  ORE.  69 

limestone  consists  of  lime,  the  oxide  of  calcium,  and  carbonic  acid; 
it  is  sometimes  mixed  with  the  oxide  of  iron,  clay,  silex,  magnesia, 
&c.  The  purer  kinds  are  known  under  the  following  terms : — 

Calcareous  Spar  occurs  in  crystals  or  crystalline  masses,  colorless 
or  white ;  dissolves  with  effervescence  in  muriatic  acid,  without  re- 
sidue ;  loses,  in  calcining,  forty-six  per  cent,  of  carbonic  acid ;  and 
turns  into  a  strong  alkaline  white  powder. 

Calc  sinter,  or  Stalactites,  are  concretions  of  limestone,  more 
impure  than  the  above  spar.  To  this  kind  of  lime  belong  alabaster 
and  calcareous  tuff. 

Travertin,  and  Spongy  Limestone  and  Chalk,  are  limestone 
mixed  slightly  with  clay. 

Marble  may  be  considered  a  pure  limestone,  and  forms  an  excel- 
lent flux  for  silicious  ores. 

Magnesian  Limestone  is  one  of  the  best  of  fluxes,  but  it  is  not  ex- 
tensively distributed  ;  there  is  excellent  magnesian  limestone  along 
the  Ohio  River,  near  Louisville.  Dolomite  belongs  to  this  class. 
Limestone  of  the  coal  formations  differs  in  the  various  beds  ;  in  the 
same  bed,  lime  of  different  purity,  often  mixed  with  iron,  magnesia, 
clay,  silex,  manganese,  &c.,  is  frequently  found. 

Oyster  Shells  form  a  very  good  flux,  and  may  be  used  where 
they  can  be  procured  in  sufficient  quantity,  and  at  reasonable  prices. 

The  composition  of  the  limestone  to  be  used  in  a  smelting  opera- 
tion ought  to  be  known  to  the  manager,  as  well  as  that  of  the  iron  ore. 
The  composition  of  iron  ore  can  be  very  frequently  guessed  at,  at 
least  so  far  as  the  ores  are  calcareous,  silicious,  or  aluminous ;  but 
with  limestone  this  cannot  be  done,  for  limestone  composed  of  fifty 
per  cent,  of  lime  and  fifty  per  cent,  of  foreign  matter,  can  hardly  be 
distinguished  from  the  pure  carbonate.  It  is  a  matter  of  very  great 
importance  that  the  manager  of  furnaces  should  know  the  exact  com- 
position of  his  limestone,  even  though  he  knows  only  superficially 
the  composition  of  the  ores.  If  calcareous  ores  are  to  be  smelted, 
it  would  be  improper  to  add  marble  (for  fluxing ;  in  these  ores,  a 
silicious  limestone  or  silicious  slate  should  be  used.  If  clay  ores 
are  the  main  material  from  which  iron  is  manufactured,  a  magnesian 
limestone  is  preferable;  but  an  aluminous  limestone  should  be  used 
where  silicious  ores  form  the  body  of  the  material. 

To  know,  at  least  qualitatively,  the  composition  of  the  limestone 
in  use,  is  of  the  utmost  necessity,  as  we  shall  hereafter  show.  And 
to  enable  the  practical  founder  to  analyze  his  limestone,  we  shall 


70  MANUFACTURE   OF  IRON. 

present  a  brief  method  of  investigating  the  qualitative  composition 
of  limestone. 

The  first  operation  is  to  weigh  a  piece  of  limestone,  or  to  take  an 
ounce  of  limestone,  burn  it  in  an  iron  pot  or  crucible,  and  weigh 
again.  If  the  limestone  loses,  in  calcining,  forty-five  or  forty- six 
per  cent.,  that  is,  -if  there  is  little  more  than  half  an  ounce  left  of 
burnt  or  quick  lime,  we  may  consider  the  specimen  pure  lime,  for 
carbonate  of  lime  is  composed  of  fifty-four  per  cent,  lime  and  forty- 
six  carbonic  acid.  If  the  specimen  loses,  in  burning,  only  twenty 
or  thirty  per  cent.,  we  may  expect  a  large  quantity  of  foreign  mat- 
ter, which  is  to  be  found  by  chemical  operations  in  the  humid  way. 

Where  we  suspect  foreign  matter  in  the  limestone,  the  burnt  spe- 
cimen should  be  moistened  with  rain  water,  and  stirred  until  pro- 
perly dissolved.  If  the  limestone  is  bad,  or  if  it  is  burnt  too  hard, 
it  may  happen  that  the  lime  will  not  dissolve  ;  but  if  the  carbonic 
acid  is  all  expelledv<which  we  find  by  adding  sulphuric,  or  any  other 
acid  to  the  lime  solution,  this  is  of  but  little  consequence.  If  the 
acid  produces  effervescence,  the  lime  is  imperfectly  burnt,  and  we 
are  then  obliged  to  burn  another  specimen,  and  proceed  in  the  same 
way,  until  an  acid  will  act  upon  it  without  producing  carbonic  acid 
gas.  If  the  lime  is  well  burnt,  no  effervescence  occurs,  and  we  may 
add  to  the  watery  hydrate  of  lime  sulphuric  acid  until  it  is  saturated, 
that  is,  until  litmus  paper  is  reddened  in  the  solution.  No  harm  is 
done  by  warming  the  whole,  and  even  boiling  it  until  no  more  acid 
is  absorbed,  and  the  solution  retains  its  acid  character.  This  solution 
is  filtered,  and  the  clear  liquid  precipitated  by  caustic  potash,  or, 
what  is  better,  by  caustic  soda;  which,  if  the  solution  is  dilute,  throws 
down  all  the  magnesia,  and  keeps  the  clay  in  solution  if  there  is 
any  dissolved ;  but  this  seldom  happens  if  the  first  solution  was 
not  boiled  too  long.  Clay,  dissolved  along  with  the  magnesia,  may 
be  precipitated  by  ammonia  or  carbonate  of  potash;  the  latter  of 
these  precipitates  with  the  clay  a  great  deal  of  potash.  In  this 
way,  if  there  is  any  magnesia,  we  find  it;  but  silex  and  clay  are 
generally  left  with  the  residue  of  lime. 

To  separate  clay  and  silex  from  the  limestone,  we  pound  the  lime- 
stone into  fine  powder,  pour  over  this  powder  strong  sulphuric  acid, 
and  boil.  The  clay,  magnesia,  iron,  and  manganese  are  dissolved 
by  adding,  gradually,  enough  water  to  keep  the  mass  liquid.  After 
we  think  all  is  dissolved  that  can  be  dissolved,  we  pour  on  more 
water,  and  add  a  surplus  of  acid;  this  prevents  the  lime  from  being 
dissolved.  The  solution  is  then  treated  with  ammonia,  when  iron 


IRON   ORE.  71 

and  all  other  matter  sink  along  with  the  clay;  or  with  caustic 
potash,  when  everything  but  the  clay  falls;  this  may  be  precipitated 
by  ammonia.  We  may  thus  approximately  find  the  amount  of  clay. 
Silex  is  yet  mixed  with  the  lime. 

If,  after  the  above  experiments,  we  suspect  that  the  main  .body 
of  foreign  matter  is  silex,  it  is  best  to  pour  over  the  pounded  lime- 
stone nitric  a<3id,  which  dissolves  everything  but  silex ;  and  we  may 
filter  and  wash  the  residue,  which  will  be  the  exact  amount  of 
silex  in  the  limestone.  The  solution  may  be  tested  by  prussiate 
of  potash,  which  precipitates  the  iron.  But  this  is  an  imperfect  test, 
inasmuch  as  clay,  manganese,  and  lime  fall  with  the  prussian  blue, 
though  they  may  be  extracted  by  boiling  with  hydrochloric  acid. 
These  are  the  simple  means  by  which  the  composition  of  limestones, 
so  far  as  is  required  for  practical  purposes,  may  be  ascertained. 
A  large  amount  of  iron  in  the  limestone  is  not  actually  hurtful,  but, 
if  we  want  to  make  gray  iron,  may  be  injurious ;  for  such  lime- 
stone is  generally  inclined  to  produce  white  iron,  and  often  black 
cinders,  in  a  hot  furnace. 

b.  Magnesia  is  an  excellent  flux  where  clay  ores  are  to  be  smelted; 
but  it  is  very  seldom  found  in  masses  sufficient  to  enable  the  iron 
master  to  use  it  for  fluxing  his  ores. 

c.  Clay,  where  it  can  be  had  of  proper  quality, is  a  most  important 
material  in  the  furnace.     It  is  to  be  applied  where  silicious  ores, 
which  furnish  weak  metal,  are  chiefly  smelted.     Lime  fluxes  well 
in  such  cases,  and  yields  gray  metal  very  readily;  but  the  metal, 
however  soft  it  may  be,  is  generally  weak.     An  addition  of  clay, 
or,  what  is  far  better,  clay  iron-stone,  will  improve  the  strength 
of  the  metal,  as  well  as  the  working  in  the  furnace.     Pure  clay,  in 
whatever  form,  is  bad ;  it  clinkers  before  the  tuyere,  and  troubles 
the  keeper.  If  a  ferruginous  clay  (red  clay)  can  be  had,  it  is  by  all 
means  to  be  preferred;  and  in  case  red  clay  contains  but  a  small  per 
centage  of  iron,  or  cannot  be  procured  at  all,  blue  clay,  which  gene- 
rally contains  more  or  less  phosphate  of  iron,  may  be  applied.    In 
the  latter  case,  however,  we  should  be  cautious  as  to  the  amount, 
for  too  much  may  injure  the  quality  of  the  metal.     Clay,  under  all 
conditions,  is  the  best  material  to  improve  the  strength  of  the  metal, 
and  deserves  attention  on  that  account. 

d.  Silex. — Calcareous  and  argillaceous  ores  generally  work  very 
badly  in  the  furnace,  whether  used  singly  or  together ;  and  are  apt 
to  furnish  white  iron.     The  best  and  only  way  to  obviate  such  evils 
is  to  add  either  silicious  slate  or  shale-     Sand  or  pure  silex  is,  like 


72  MANUFACTURE   OF  IRON. 

pure  clay,  not  to  be  recommended.  If  ferruginous  shale  is  to  be 
used  for  fluxing,  the  shale  or  slate  must  be  roasted  or  burnt  like  ore, 
until  all  bitumen  is  expelled  ;  and  the  iron,  which  is  generally  in 
the  form  of  protoxide,  is  oxidized  into  peroxide.  If  ferruginous 
silex  is  added  to  the  ore  charges  in  this  way,  the  result  is  generally 
favorable. 

e.  Another  flux,  which  influences  the  progress  of  the  smelting  ope- 
rations, besides  the  artificial  fluxes,  and  the  foreign  matter  in  the  ores, 
is  the  matter  contained  in  the  fuel,  the  ashes ;  these  form  accidental 
fluxes,  but  are  of  importance  in  the  operation.  The  ashes  of  wood, 
and  charcoal  of  wood,  generally  contain  a  preponderating  amount 
of  alkali.  This  alkali  may  be  considered  beneficial  as  an  electro- 
positive agent  of  fluxing,  and  facilitates  the  reviving  of  metal,  as 
well  as  the  fluidity  of  the  slag,  where  the  mixture  of  ores  and  arti- 
ficial fluxes  is  composed  of  a  predominating  amount  of  silex  and 
clay.  The  ashes  of  mineral  coal  and  anthracite  contain  principally 
silex  and  clay,  and  may  be  considered  electro-negative.  They  will 
be  fluxes  where  the  ores  contain  a  preponderance  of  lime,  magnesia, 
or  of  the  alkalies.  How  far  such  matters  have  any  influence  upon 
the  success  of  smelting  operations,  will  be  shown  in  another  place. 

XXII.  Assay  of  Iron  Ores. 

Where  our  only  object  is  to  separate  exactly  the  amount  of  iron 
contained  in  a  given  specimen  of  ore,  without  reference  to  foreign 
matter,  we  apply  the  dry  method  in  the  assay  of  the  ore.  In 
order  to  succeed  in  this  operation,  we  must  deoxidize  the  oxide  of 
iron,  and  produce,  at  the  same  time,  a  temperature  sufficiently  high 
to  melt  the  revived  metal,  as  well  as  to  melt  the  earth  associated 
with  the  ore,  together  with  the  flux.  The  former  may  be  obtained 
in  a  dense  button  on  the  bottom  of  the  crucible,  and  the  latter  in  a 
liquid  slag  or  glass  above  it.  The  foreign  matter  contained  in  the 
ore  is  generally  silex,  lime,  clay,  &c.  These  are,  in  themselves,  very 
refractory ;  hence  some  flux  is  necessary  to  bring  about  their  fusion. 
Fluxes,  generally  employed  in  operating  on  this  small  scale,  are 
borax,  flint-glass,  lime,  or,  what  are  the  best  of  all,  carburetted 
alkalies.  The  last  are  produced  by  burning  or  calcining  the  tar- 
trates  along  with  saltpetre.  In  these,  as  well  as  in  large  operations, 
we  are  guided  by  the  electrical  character  of  the  matter  mixed  with 
the  ore  ;  we  must  mix  alkalies  with  clay,  or  silicious  ores,  and  acids 
along  with  calcareous  ore.  Nevertheless,  borax,  in  almost  all  cases, 
melt  the  foreign  matter  into  a  slag. 


IRON  ORE.  73 

The  ore  to  be  analyzed,  say  one  hundred  grains,  is  pulverized, 
and  passed  through  a  fine  silk  sieve,  mixed  with  the  flux,  which 
is  to  be  in  powder  also,  and  intimately  rubbed  together  with  the  ore. 
Where  borax  is  applied,  it  should  be  either  dried  or  melted,  that 
the  water  of  crystallization  may  be  expelled,  which,  if  not  previously 
effected,  is  very  apt  to  break  the  crucible,  or  to  raise  the  whole  mass 
over  its  brim.  The  mixture  of  flux  and  ore  is  introduced  into  the 
smooth  concavity  made  in  the  centre  of  a  crucible,  lined  with  hard 
rammed  and  damp  charcoal  dust.  The  ore  should  not  be  mixed 
with  carbon,  for  carbon  frequently  prevents  the  separation  of  the 
slag,  and  the  sinking  of  the  metal.  The  mixture  should  be  well 
covered  with  charcoal,  and,  if  possible,  with  a  lid  luted  with  fire 
clay.  The  crucible,  thus  fitted  up,  is  set  on  its  base  either  in  an 
air-furnace,  heated  with  coke  or  charcoal,  or  in  the  hearth  of  a 
smith's  forge,  urged  with  a  smith's  bellows.  The  heat  should  not 
be  urged  until  after  the  lapse  of  a  quarter  or  of  half  an  hour ;  this 
time  is  required  to  expel  the  moisture  in  the  charcoal  and  the  ore. 
At  the  end  of  this  period,  the  heat  may  be  gradually  raised  to  the 
melting  point  of  iron,  and  maintained  for  a  quarter  of  an  hour,  after 
which  the  crucible  may  be  withdrawn,  and  slowly  cooled.  When- 
ever the  crucible  is  sufficiently  cool,  it  may  be  opened  by  removing 
the  lid,  the  remaining  coal  dust,  and  the  slag.  The  button  of  metal 
will  be  found  at  the  bottom  of  the  crucible,  and  may  be  taken  out 
and  weighed ;  its  weight  in  grains,  in  case  one  hundred  grains  of 
ore  have  been  originally  taken  for  the  experiment,  will  give  exactly 
the  per  centage  of  iron  in  the  ore.  The  assay  in  this  way  always 
succeeds  best  if  we  calcine  the  ore  before  smelting,  that  is,  if  we 
expose  the  powdered  ore  to  a  red  heat  before  mixing  it  with  the 
flux. 

A  far  more  secure  way  of  success  in  assaying  ore  by  the  dry 
method  is  to  mix  the  powdered  and  calcined  ore  along  with  cyanide 
of  potassium,  and  then  to  proceed  as  above.  This  mixture  never 
fails  to  furnish,  by  a  low  temperature,  a  button  of  gray  metal. 

If  an  assay  of  ore  is  required  where  not  only  the  amount  of  iron, 
but  the  quantity  and  quality  of  the  foreign  matter,  are  unknown,  the 
operation  becomes  more  complicated,  and  it  is  necessary  to  pro- 
ceed in  the  humid  way.  If  we  know  nothing  of  the  composition 
of  the  ore,  nor  even  suspect  the  presence  of  any  particular  sub- 
stance besides  iron,  we  proceed  according  to  the  following  method  : 
The  iron  ore,  say  one  hundred  grains,  is  powdered,  and  passed 
through  a  silk  sieve ;  it  is  then  digested  with  water,  and  hot 


74  MANUFACTURE   OF  IRON. 

nitre-muriatic  acid  poured  over  it ;  this  acid  will  dissolve  every- 
thing but  silex ;  and  in  many  cases  it  will  even  dissolve  silex,  par- 
ticularly in  magnetic  and  calcareous  ores.  However,  an  excess 
of  the  acid  generally  prevents  its  solution  along  with  the  alkaline 
oxides.  If  the  solution  is  completed  by  boiling,  lime,  magnesia, 
clay,  iron,  manganese,  &c.,  will  probably  be  dissolved,  and  silex 
remain  undissolved;  this  may  be  washed,  dried,  and  weighed. 
Oxalate  of  ammonia,  added  to  a  few  drops  of  the  solution,  dilut- 
ed with  water,  will  indicate  the  presence  of  lime  by  precipitating 
oxalate  of  lime  in  a  white  powder.  In  the  same  way,  magnesia 
may  be  detected  by  basic  phosphate  of  ammonia,  which  precipitates 
phosphate  of  ammonia  and  magnesia,  even  in  a  very  weak  solution, 
by  stirring  it  with  a  glass  rod.  In  the  concentrated  acid  solution, 
clay  may  be  detected  by  adding  some  sulphate  of  potash  in  powder, 
which  dissolves  or  increases  in  bulk ;  in  the  latter  case,  it  forms 
alum  in  crystals,  which  may  be  separated  and  dissolved  in  water. 
Caustic  ammonia  will  precipitate  alumina  from  this  solution.  Man- 
ganese cannot  be  detected  until  the  iron  is  separated  ;  this  separa- 
tion can  be  accomplished  in  the  following  manner :  Dilute  a  few 
drops  of  the  original  solution  with  water,  and  precipitate  the  iron 
by  means  of  a  solution  of  galls  ;  then  filter ;  take  the  clear  liquid, 
and  precipitate  by  caustic  potash  or  soda  :  if  manganese  is  present, 
a  white  precipitate  falls,  which  alters  its  color  by  degrees  into  yel- 
low, brown,  and,  finally,  when  exposed  to  the  influence  of  air, 
black.  The  presence  of  sulphur  or  phosphorus  cannot  be  ascer- 
tained in  this  way ;  but  carbonic  acid  will  rise  in  bubbles  when 
the  acid  is  poured  over  the  ore ;  and  if  we  intend  to  determine  the 
amount  of  carbonic  acid,  the  calcining  of  the  ore  powder  is  required 
before  it  is  dissolved.  The  loss  of  weight  in  this  operation,  with 
due  allowance  for  the  alteration  from  protoxide  to  peroxide,  will 
give  the  amount  of  water  and  carbonic  acid.  The  foregoing  mani- 
pulation will  give  the  qualitative  analysis  of  the  ore ;  but  if  the 
quantity  of  matter  in  the  ore  composition  is  required,  the  following 
method  must  be  pursued  : — 

Take  a  mixture  of  caustic  potash  and  caustic  soda,  each  one 
hundred  grains,  and  melt  both  together  in  a  platina  or  silver  cru- 
cible ;  then  throw  in,  by  degrees,  continually  stirring,  the  one  hun- 
dred grains  of  powdered  ore.  The  alkali  will  dissolve  silex,  clay, 
the  sulphurets,  and  phosphurets,  and  leave  oxide  of  iron,  manganese, 
lime,  and  magnesia,  undissolved.  The  solution  may  be  filtered, 
and  the  residue  dissolved  in  strong  sulphuric  acid,  which  dissolves 


IRON    ORE.  75 

the  oxide  of  iron,  magnesia,  and  manganese.  Lime  is  left  as  a 
white  powder,  sulphate  of  lime,  gypsum.  From  the  acid  solution, 
magnesia  may  be  precipitated  by  basic  phosphate  of  ammonia ;  the 
sediment,  washed  and  calcined,  leaves  phosphate  of  magnesia.  The 
remainder  of  the  acid  solution  contains  iron  and  manganese,  which 
are  to  be  separated  by  gallic  or  succinic  acid,  which  precipitates 
the  iron.  This  sediment  may  be  calcined,  which  leaves  oxide  of 
iron.  The  manganese  is  to  be  precipitated  by  caustic  potash  or 
soda  ;  filtered,  and  dried.  In  this  way  we  get  the  amount  of  iron 
in  oxide  of  iron ;  the  manganium  in  manganese  ;  magnesia  in  phos- 
phate of  magnesia ;  and  the  lime  in  sulphate  of  lime.  The  alkaline 
solution  of  silex  and  clay  is  to  be  saturated  with  sulphuric  acid, 
which  precipitates  the  silex  in  a  white  powder ;  this  is  to  be  washed 
and  dried.  The  remaining  clay  is  yet  held  in  solution,  and  may 
be  precipitated,  after  neutralizing  first  with  caustic  potash,  by  car- 
bonate of  ammonia.  If  sulphur  is  in  the  ore,  it  may  be  detected 
by  the  smell  of  sulphuretted  hydrogen,  when  pouring  the  acid  on 
the  alkaline  solution,  or  may  be  previously  tested  by  acetate  of 
lead.  Phosphorus  may  be  detected  by  letting  fall  a  few  drops  of 
the  alkaline  solution  into  some  lime-water,  when  phosphate  of  lime 
is  precipitated,  provided  there  is  no  carbonic  acid  present ;  this  can 
be  ascertained  by  testing  the  white  precipitate  by  hydrochloric  acid, 
which  dissolves  the  carbonate  of  lime,  but  not  the  phosphate,  if 
there  is  no  excess  of  acid. 

A  quantitative  chemical  analysis  is  very  seldom  insisted  upon  by 
the  iron  manufacturer,  and  is  not  generally  considered  to.be  actually 
needed.  This  may  be,  in  some  measure,  true :  but  a  qualitative 
analysis  is  almost  necessary  in  every  case.  A  good  manager  should 
be  able  to  determine  at  least  the  quality  of  the  matter  of  which  his 
ore  is  composed.  An  anaylsis  of  this  kind  is  very  easily  effected ; 
and  we  shall  describe  a  simple  method  by  which  the  component 
parts  of  any  kind  of  iron  ores  may  be  discovered. 

Iron  ores  are  of  various  colors,  and  occur  in  the  most  various 
forms.  The  following  is  the  most  simple  test  by  which  a  given 
specimen  of  mineral  may  be  determined  :  Put  it  into  a  slow  burn- 
ing fire,  say  a  common  grate  fire,  and  there  leave  it  for  twenty- 
four  hours.  If,  at  the  expiration  of  that  period,  it  shall  have  turned 
red  or  brown,  it  may  be  considered  iron  ore.  We  may  also  con- 
clude that  it  is  iron  ore  when,  in  turning  black,  some  fragments  of  it 
are  attracted  by  the  magnet.  If  the  substance  shall  have  turned 
white,  it  will  be  either  wholly  or  in  greater  part  lime;  which,  how- 


76  MANUFACTURE   OF   IRON. 

ever,  may  be  very  useful  under  circumstances  where  calcareous  ore  is 
needed.  This  is  an  easy  practical  method  of  arriving  at  an  esti- 
mate of  a  mineral  species;  but,  with  the  exception  of  the  iron  it  con- 
tains, leaves  us  quite  in  the  dark  as  to  its  component  parts.  If  any 
specimen  is  proved  to  contain  iron  in  sufficient  quantity  to  justify 
the  manufacturer  in  smelting  it,  it  is  of  great  consequence  to  know 
the  foreign  matter  associated  with  it.  To  determine  this  point,  we 
proceed  as  follows  : — 

Sulphur  exists  in  most  iron  ores,  particularly  the  hydrates,  either 
in  the  form  of  sulphates  or  sulphurets.  To  find  sulphur,  a  portion 
of  ore  is  pounded  and  passed  through  a  fine  silk  sieve,  and  then 
washed  with  a  large  quantity  of  rain  water,  which  must  be  previ- 
ously freed  of  sulphuric  acid  by  chloride  of  barium.  The  wash- 
water  of  the  powder,  which  may  be  boiled  with  the  ore,  is  set  to 
rest,  that  the  iron  may  subside ;  and  part  of  it  is  then  tested  with 
chloride  of  barium.  If  a  white  precipitate  falls,  we  may  conclude 
that  the  ore  contains  sulphuric  acid.  In  some  ores,  particularly  the 
yellow  hydrates,  sulphuric  acid  is  not  so  readily  detected.  In  such 
cases,  we  must  dry  the  washed  powder,  and  expose  it  to  a  gentle 
heat  until  it  reddens,  and  again  pour  it  into  the  water.  If,  after  this, 
it  shows  no  signs  of  a  precipitate  with  chloride  of  barium,  we  may 
conclude  that  no  sulphuric  acid  is  present.  Chlorine  is  found  in 
the  same  way,  with  the  only  difference  that  we  use  nitrate  of  silver 
as  a  precipitant.  If  a  white  precipitate  falls  directly,  we  may  ex- 
pect that  the  ore  contains  a  large  amount  of  chlorine.  But  a  small 
quantity  of  chlorine  will  manifest  itself  only  after  one  or  two  days' 
exposure  of  the  solution  to  light,  when  it  will  gradually  darken 
from  violet  to  black.  We  may  expect  to  find  sulphuric  acid  and 
chlorine  in  the  hydrates  of  the  coal  formation.  Sulphur,  in  the 
form  of  sulphurets,  may  be  detected  by  boiling  the  powder  of  iron 
ore  in  a  solution  of  potash,  which  dissolves  the  sulphurets ;  and  by 
testing  that  solution,  when  clear,  with  acetate  of  lead.  If  there  is 
any  sulphur  in  the  ore,  a  black  precipitate  of  sulphuret  of  lead 
will  form  directly. 

The  powder  of  ore,  thus  freed  from  sulphuric  acid,  chlorine,  and 
sulphur,  may  now  be  dissolved  in  hydrochloric  acid ;  this  acid  will 
dissolve  everything  but  sulphate  of  baryta,  sulphate  of  lime,  silex, 
and  carbon.  Carbonic  acid  will  escape  with  effervescence,  and  is 
easily  detected.  If  the  insoluble  residue  is  white,  we  may  expect  in 
it  sulphate  of  baryta,  silex,  and  a  little  alumina.  It  cannot  contain 
sulphate  of  lime,  for,  as  this  is  soluble  in  water,  it  would,  of  course, 


IRON   ORE.  77 

in  our  first  experiment,  have  been  decomposed  by  chloride  of  barium. 
The  residue  may  be  melted ;  fused  with  four  times  its  weight  of  a 
mixture  of  carbonate  of  potash  and  soda,  in  a  silver  or  polished  iron 
crucible  ;  soaked  in  water,  boiled,  and  filtered  ;  and  then  saturated 
with  hydrochloric  acid.  If  a  precipitate  falls,  it  is  silex  ;  while  the 
remaining  portion  of  the  dissolved  residue  must  be  sulphate  of  baryta. 
Different  soluble  compounds  may  now  be  employed  to  test  the  first 
hydrochloric  solution.  The  application  of  oxalate  of  ammonia  to  a 
few  drops  of  this  solution,  largely  diluted  with  water,  will  show 
the  presence  of  lime ;  and  caustic,  or  carbonate  of  ammonia,  that  of 
alumina  and  chromium.  Sulphuric  acid  will  precipitate  barytes 
and  lead.  A  bright  iron  wire,  or  blade  of  a  knife,  held  in  the 
solution  for  a  short  time,  will  show  the  presence  of  copper,  by 
giving  a  coating  of  copper  to  the  polished  iron.  Magnesia  it  is 
somewhat  difficult  to  detect ;  but,  if  it  is  not  in  too  small  amount, 
it  may  be  detected  by  boiling  the  solution,  from  which  baryta  and 
lime  have,  by  the  above  tests,  been  previously  removed,  with  car- 
bonate of  soda ;  but  more  effectually,  if  we  precipitate  all  the  sub- 
stances in  a  part  of  the  solution  by  carbonate  of  ammonia,  and  re- 
move the  baryta  by  sulphuric  acid,  and  the  lime  by  oxalate  of  am- 
monia, neutralize  by  ammonia,  and  then  precipitate  by  phosphate 
of  soda,  which  throws  down  a  basic  phosphate  of  ammonia  and  mag- 
nesia. Acetate  of  lead  is  a  very  valuable  reagent ;  it  forms  with  any 
of  the  chromic  solutions  a  yellow  precipitate;  with  phosphoric  acid  a 
white,  and  with  sulphur  a  black,  precipitate:  but  with  a  hydrochloric 
solution,  it  would  form  a  white  sediment  of  chloride  of  lead  soluble  in 
excess  of  potash;  while  the  sulphuret,  chromate,  and  phosphuret  are 
insoluble  in  that  menstruum.  If  there  is  any  zinc  in  the  ore,  it  may 
be  found,  after  the  iron  is  precipitated,  by  sulphuretted  hydrogen,  pro- 
vided the  solution  is  previously  neutralized;  this  precipitates  a  white 
sulphuret  of  zinc.  For  the  purpose  of  detecting  zinc,  it  is  neces- 
sary to  remove  iron  and  everything  else,  by  saturating  the  acid 
solution  by  ammonia,  and  by  then  testing  with  sulphuretted  hydro- 
gen. The  most  common  compounds  in  iron  ore  are  yet  left  to  be 
found  ;  these  are  manganese  and  phosphorus.  Manganese  is  with 
difficulty  separated  from  iron  ;  and  to  effect  this  separation,  we 
recommend  the  solution  of  the  iron  ore  in  hydrochloric  instead 
of  nitro-hydrochloric  acid,  because  in  the  latter  case  the  salts  of 
manganese  are  very  apt  to  oxidize  more  highly  than  protoxide,  and 
are  then  inseparable  from  iron.  If  the  solution  of  the  ore  is  acidulous, 


78  MANUFACTURE   OF  IRON. 

the  manganese  will  be  in  the  form  of  protochloride  of  manganese, 
and  may  be  separated  from  the  iron  by  boiling  the  solution  to  dry- 
ness,  and  by  expelling  all  the  superfluous  acid.  On  redissolving  it  in 
water,  only  the  salts  of  alkalies  and  alkaline  earths  will  be  dissolved 
along  with  the  manganese,  and  very  little  of  the  iron  ;  this  iron  may 
be  precipitated  by  succinic  or  benzoic  acid,  provided  the  solution  is 
neutral.  After  this  we  may  detect  iron  by  means  of  ferrocyanide 
of  potassium,  which,  if  the  iron  is  all  removed,  ought  not  to  change 
the  color  of  the  solution,  but  form  a  white  precipitate  with  manga- 
nese. In  a  solution  free  from  iron,  the  manganese  will  be  preci- 
pitated by  ammonia  or  carbonate  of  ammonia,  which  throws  down 
a  double  salt  of  manganese  and  ammonia.  For  the  same  reason 
as  that  given  above,  we  recommend  the  solvent,  hydrochloric  acid, 
in  an  iron  ore  analysis,  as  the  means  of  detecting  phosphorus.  The 
hydrochloric  solution  of  iron^  &c.,  may  be  neutralized  by  ammonia, 
which  separates  the  earths  and  a  part  of  the  iron,  but  leaves  the 
phosphates  in  solution.  The  solution  may  be  tested  by  chloride  of 
barium,  which  produces  in  a  neutral  or  alkaline  solution  a  white 
precipitate  of  phosphate  of  barytes  ;  this  is  redissolved  by  adding 
hydrochloric  or  nitric  acid.  Other  foreign  matter  in  iron  ores  is  of 
little  consequence,  and  need  not  be  taken  into  consideration. 

Those  acquainted  with  the  use  of  the  blowpipe  are  able  to  detect 
sulphur,  phosphorus,  arsenic,  zinc,  and  other  substances,  more  easily 
with  that  instrument  than  by  any  other  means;  but  no  directions  are 
needed  to  guide  their  manipulation,  for  we  shall  assume  them  to 
be  masters  on  this  subject. 

Poor  ores,  particularly  clay  ores,  are  sometimes  difficult  of  assay, 
even  though  we  simply  want  to  know  the  amount  of  iron  contained  in 
them.  The  clay  ores  require  an  uncommon  amount  of  alkaline  flux, 
and  lime  is  not  sufficiently  strong  to  flux  the  alumina  ;  we  are  there- 
fore compelled  to  make  use  of  potash  or  soda.  Both  are  very  apt  to 
perforate  the  crucible.  A  mixture  of  potash  and  borax  answers 
better  ;  but  if  too  small  a  portion  is  used,  all  the  iron  is  not  revived ; 
and  if  too  much,  the  crucible  is  destroyed  before  the  iron  begins  to 
melt.  In  such  cases,  the  best  plan  is  that  prescribed  by  Fresenius, 
that  is,  to  mix  the  powdered  and  calcined  ore  with  cyanide  of  potas- 
sium, and  to  smelt  the  ore,  and  revive  the  iron,  in  a  porcelain  or  pla- 
tinum crucible,  over  a  spirit-lamp,  in  which  case  an  excess  of  the  flux 
is  of  but  little  danger.  This  mode  of  analyzing  is  particularly  use- 
ful where  arsenic  is  combined  with  the  ore,  for  it  will  reduce  the 


IRON   ORE.  79 

oxides  of  that  metal  in  the  most  easy  way.  The  arsenic  may  be 
separated  before  melting  the  iron,  or,  if  more  arsenic  is  present  than 
that  required  to  form  an  arseniate  of  iron,  it  may  be  evaporated  by 
heating  to  ignition  in  a  glass  tube.  Otherwise,  the  latter  compound 
will  remain  in  the  crucible. 


80  MANUFACTURE   OF   IRON. 


CHAPTER  II. 

FUEL. 

Remarks. — It  does  not  belong  to  our  department  to  consider  the 
many  substances  used  to  produce  artificial  heat.  Of  these  chem- 
istry treats.  We  shall  speak  of  those  vegetables  and  minerals 
alone  which  afford  proper  fuel  for  the  manufacture  of  iron. 

I.    Wood. 

Wood,  in  its  raw  state,  does  not  constitute  an  available  fuel, 
because  it  contains  a  large  amount  of  water.  This  water  contains 
more  or  less  soluble  minerals,  and  is  called  sap.  By  drying  wood, 
a  great  part,  but  not  all,  of  this  water  is  evaporated.  If  wood  is 
dried  in  a  closed  vessel,  and  then  exposed  to  the  atmosphere,  it 
quickly  absorbs  moisture ;  but  the  moisture  thus  absorbed  is  much 
less  than  the  wood  originally  contained. 

a.  The  amount  of  water  varies  in  different  kinds  of  wood,  and 
also  varies  according  to  the  season.  Wood  cut  in  the  month  of 
April  contains  from  10  to  20  per  cent,  more  water  than  that  cut  in 
the  month  of  January. 

The  following  table  shows  the  per  centage  of  water  in  different 
kinds  of  wood,  dried,  as  far  as  possible,  in  the  air. 

37.0 

38.2 
39.0 
45.5 
47.1 

48.2 
51.8 

"Wood,  cut  during  the  months  of  December  and  January,  is  not 
only  more  solid,  but  it  will  dry  faster,  than  at  any  other  period  of 
the  year,  because  the  sap  by  that  time  has  incorporated  a  great  part 
of  its  soluble  matter  with  the  woody  fibre  ;  what  remains  is  merely 
water.  When  the  sap,  during  the  months  of  February,  March,  and 


Beech 

18.6 

Pine,  white 

Poplar 

26.0 

Chestnut     - 

Sugar,  and  common 

Maple  27.0 

Pine,  red    - 

Ash 

28.0 

Pine,  white 

Birch 

30.0 

Linden 

Oak,  red     - 

34.7 

Poplar,  Ital. 

Oak,  white 

35.5 

Poplar,  black 

FUEL.  .       81 

April,  rises,  it  partly  dissolves  the  woody  fibre;  and  the  drying  of 
the  wood  is  not  only  retarded,  but  the  wood  is  weakened,  in  conse- 
quence of  the  solid  matter  thus  held  in  solution. 

b.  Hard  and  Soft  Wood  are  terms  which,  for  our  purpose,  have 
no  useful  application.     The  difference  in  chemical  composition  of 
the  woody  fibre,  in  most  kinds  of  wood,  is  but  slight,  as  the  follow- 
ing analytical  table  shows  : — 

Carbon.  Hydrogen.  Oxygen. 

Sugar  maple  -  52.65  5.25  42.10 

Oak     -  -  49.43  6.0T  44.50 

Poplar,  black  -  49.70  6.31  43.99 

Pine    -  -  50.11  6.31  43.58 

c.  Of  far  greater  importance  to  the  manufacturer  of  iron  is  the 
specific  gravity  of  the  different  kinds  of  wood.     This  is  the  proper 
criterion  of  their  value,  because  wood  is  generally  bought  by  mea- 
surement ;  and  its  specific  gravity  is  directly  in  proportion  to  its 
amount  of  carbon,  hydrogen,  and  oxygen ;  and  the  carbon  and 
hydrogen  constitute  fuel.     The  following  table  shows  the  specific 
gravity  of  wood.     Water  =1.000  : — 

Green.  Air-dried.  Kiln-dried. 

Oak,  white    -  -  1.0754  0.7075  0.663 

Oak,  red       -  -  1.0494  0.6777  0.663 

Poplar  -  0.9859  0.4873  0.4464 

Beech  -  0.9822  0.5907  0.5788 

Sugar  maple  -  0.9036  0.6440  0.6137 

Birch  -  0.9012  0.6274  0.5699 

Pine,  red      -  -  0.9121  0.5502  0.4205 

Pine,  white  -  0.8699  0.4716  0.3838 

Ebony  "  1.2260  " 

Guaiac  (lignum  vitse)     -  "  1.3420  « 

The  value  of  wood  by  measure  corresponds  directly  with  its  spe- 
cific gravity  after  being  dried  in  the  kiln.  Oak  is,  therefore,  worth 
nearly  as  much  again  as  white  pine,  for  making  charcoal.  This 
subject  deserves  the  close  attention  of  the  iron  master,  for  it  is  his 
business  to  select  wood,  and  to  regulate  its  price  according  to  its 
quality. 

d.  Jlshes. — The  remains  of  wood  after  combustion,  denominated 
ashes,  are  of  far  greater  importance  than  we  should  at  first  be  in- 
clined to  believe.     In  the  progress  of  this  work,  we  shall  find  that 
the  production  of  iron  from  the  ore  depends,  in  a  great  measure, 

6 


82  MANUFACTURE   OF  IRON. 

on  the  quality  and  quantity  of  alkali  present ;  and  we  shall  farther 
find  that  even  the  mechanical  form  of  the  alkali  is  of  consequence 
in  the  reduction  of  the  ore.  It  is,  therefore,  of  no  small  importance 
to  pay  due  attention  to  the  constitution  of  wood,  in  consideration  of 
the  amount  and  quality  of  ashes  it  contains.  It  is  of  more  conse- 
quence to  know  the  amount  of  fixed  alkali  in  the  ashes  than  the 
quantity  of  mineral  acids,  because  the  former  always  predominates 
in  wood,  while  the  latter  is  so  insignificant  that  it  may  he  neglected. 
The  alkali  contained  in  wood  is  mostly  potash,  for  soda  is  in  so 
small  a  quantity,  that  it  interferes  very  slightly  in  our  calculations. 
We  give  the  amount  of  potash  contained  in  1000  parts  of  wood  of 
different  kinds,  cut  during  winter  and  dried  : — 


Corn  stalks                   -  17,50 

Sunflower  stalks            -  20.00 

Thistles,  in  full  growth  35.37 
Straw  of  wheat,  before  > 
earing                          ; 

Wormwood            -         -  79.00 


Pine  or  fir  -                 -  0.45 

Poplar  -  0.75 

Beech  -  1.45 

Oak  -  1.53 

Willow  -  2.85 

Maple  -  3.90 

Dry  beech  bark      -         -  6.00 

Besides  potash,  a  large  amount  of  lime  commonly  exists  in  wood 
ashes.  Lime  is  very  favorable  to  the  reduction  of  iron  ores,  and 
deserves  attention.  It  is  generally  understood  that  the  potash  or 
soda  which  exists  in  the  ashes  of  plants  is  always  in  an  inverse 
proportion  to  the  amount  of  lime  they  contain.  We  give,  in  the 
following  analyses,  a  comparative  view  of  the  amount  of  lime  in 
100  parts  of  different  vegetable  ashes  : — 


Beech. 

Oak. 

Pine. 

Bark  of  oak. 

Carbonic  acid           38.18 

31.30 

18.09 

38.67 

Sulphuric  acid            1.19 

0.90 

3.75 

0.37 

Hydrochloric  acid      0.85 

0.62 

0.00 

0.04 

Silicious  acid  (silex)    3.38 

1.67 

7.59 

1.08 

Phosphoric  acid         4.77 

6.27 

0.90 

Potash                       10.45 

9.43 

16.80 

4.33 

Lime                         35.66 

39.95 

34.67 

47.78 

Magnesia                    5.86 

7.15 

4.35 

0.75 

Oxide  of  iron             1.25 

0.09 

11.15 

manganese  3.77 

2.60 

2.75 

6.98 

The  amount  of  ashes  differs  in  different  plants,  as  the  following 


FUEL. 


table  indicates,  and  varies  strikingly  in  trees  and  shrubs,  and  in 
trunks  and  leaves.     There  are,  in  100  parts  of  air-dried 


Oak  wood       (  old> 

I  young,  0.15 

-p.    ,          ,      fold,  0.30 
Birch  wood     < 

I  young,  0.25 

Blackberry,  2.60 


TV  A  /°ld>  °'15 

Pine  wood      < 

I  young,  0.12 

T>      ,          ,     fold,        0.40 
Beech  wood    < 

I  young,  0.37 

Wheat  straw,  5.20 


The  amount,  as  well  as  the  composition  of  ashes,  depends,  in  a 
great  measure,  upon  the  composition  of  the  soil  in  which  the  plant 
grows.  But  if  the  chemical  composition  of  the  soil  is  not  able  to 
furnish  the  vital  component  parts  of  a  certain  genus  of  plants,  this 
genus  will  decay,  and  its  place  will  be  occupied  by  a  class  more 
appropriate  to  this  composition.  For  this  reason  we  often  see  oak 
growing  where  pine  has  been  cut,  and  weeds  spring  up  where  none 
have  been  sown. 

The  ashes  of  a  pine  tree,  in  one  place,  have  contained 

Potash    -  3.66 

Lime      -  ....      46.34 

Magnesia        -  -        -         6.77 

While  ashes  of  the  same  kind  of  pine,  growing  in  another  spot, 
have  furnished  the  following  result: — 

Potash    -  ....         7.36 

Lime      -  -       51.19 

Magnesia        ...  none. 

e.  Practical  Remarks. — The  foregoing  investigations  and  tables 
are  only  designed  to  present  to  the  iron  manufacturer  a  comparative 
view  of  the  relative  values  of  wood.  Therefore  his  attention  should 
be  closely  directed  to  the  material  best  adapted  for  his  purposes. 
We  have  seen  that  there  is  a  great  difference  in  the  specific  gravity 
of  wood;  and  that  the  price  per  cord  should  vary  in  accordance  with 
this  difference.  That  is  to  say,  if  a  cord  of  pine  wood  is  worth 
thirty-eight  cents,  then  a  cord  of  oak  ought  to  be  worth  sixty-six 
cents,  because  it  is  the  real  woody  fibre  which  constitutes  fuel,  and 
it  is  that  which  produces  charcoal.  Besides  the  attention  which 
the  specific  gravity  of  wood  demands,  the  consideration  whether 
wood  is  old  or  young  is  very  important.  Young  wood,  saplings,  if 
properly  treated,  generally  produce  a  strong  hard  coal ;  old  wood, 
when  sound,  is  not  inferior;  but  dead  or  decayed  wood  is  useless 
for  the  making  of  charcoal,  and  it  is  imperfect  fuel  for  any  purpose. 


84  MANUFACTURE  OF  IRON. 

Therefore  a  higher  price  may  be  paid  for  young  than  for  the  same 
kind  of  old  wood,  when  other  circumstances  are  equal. 

Every  attention  should  be  paid  to  the  proper  season  for  cutting 
wood.  The  worst  time  is  from  February  until  September.  It 
should  be  cut  and  corded  in  October,  November,  December,  and 
January;  the  best  time  is  in  the  two  latter  months.  Wood  cut 
during  winter,  besides  being  ripe,  will  dry  fast,  and  furnish  a  strong 
sound  coal.  Wood  that  is  fresh  and  green  is  very  apt  to  crack  in 
charring,  and  produces  a  small  porous  coal,  unfit  for  use  in  the 
blast  furnace.  Besides,  economy  recommends  the  use  of  the  winter 
months,  for  then  workmen  are  more  abundant,  and  wood  is  twenty- 
five  per  cent,  more  valuable. 

The  price  paid  per  cord  for  cutting  wood  varies  according  to  place 
and  time.  While  a  woodcutter  in  Vermont  is  able  to  make  good 
wages  at  twenty-five  cts.  per  cord,  the  cutter  in  Missouri  thinks 
double  that  amount  poor  compensation.  From  twenty  to  twenty- 
five  per  cent,  more  is  paid  for  saplings,  and  crooked  or  thinly  grown 
timber,  than  for  common  forest  timber.  Tall,  and  tolerably  strong 
timber,  where  the  trees  do  not  average  less  than  twelve  nor  more 
than  twenty-four  inches  in  diameter,  yields  the  most  profitable  results. 
Hardened  wood,  maple,  sycamore,  and  knotty  timber  are  more 
expensive  than  oak,  beech,  hickory,  pine,  and  tall,  clear  timber. 
Hillsides  are  cleared  with  more  difficulty  than  plains,  and  demand 
higher  wages.  A  good  woodcutter  ought  to  average  three  cords 
a  day.  Some  will  cut  more,  some  less,  according  to  their  industry 
and  ability;  and  wages  ought  to  be  rated  accordingly. 

A  cord  of  wood  contains  128  cubic  feet;  that  is,  the  billets  must 
be  four  feet  long,  and  the  cord  four  feet  high  and  eight  feet  long.  A 
great  deal  of  deception  is  practiced  by  workmen,  who  need  close 
watching.  The  most  common  deceptions  are  these:  the  billets  too 
short;  the  cords  deficient  in  length  and  height;  crooked  rows; 
piling  the  wood  upon  rocks  or  upon  stumps;  long  limbs  on  the 
billets ;  and  piling  the  billets  in  as  open  a  manner  as  possible. 
These  deceptions  are  easily  detected.  They  often  amount  to  twenty- 
five  or  thirty  per  cent.  Such  practices  should  be  avoided  in  a  well- 
regulated  business.  Managers  are  often  as  much  at  fault  as  the 
workmen;  for  many  of  them,  by  making  it  a  rule  to  dock  the  work- 
men rightly  or  wrongly,  necessarily  provoke  resistance,  and  excite 
cupidity. 

An  acre,  of  160  square  rods,  contains,  on  an  average,  thirty  cords 
of  wood;  sometimes  more,  sometimes  less.  It  requires  excellent 


FUEL.  85 

timber  to  produce  forty  cords;  and  only  very  close  timber  will  exceed 
that.  The  price  of  wood  on  the  ground  ranges  from  five  to  ten  cents 
per  cord ;  and  it  is  clear  that  in  many  cases  five  cents  may  be  too 
much,  and  in  other  cases  ten  cents  may  be  too  little,  for  certain  wood. 
The  best  timber  is  always  the  cheapest,  although  it  commands  a 
higher  price.  Where  clearings  are  designed,  the  stumps  ought  to 
be  cut  as  low  as  possible,  the  brush  piled,  and,  when  practicable, 
burnt  before  charring  commences,  in  order  that  a  way  for  hauling 
the  wood  to  the  pits  may  be  opened.  Hillsides,  rocks,  and  swamps, 
as  well  as  detached  patches,  make  the  wood  and  coal  dear.  There 
should  be  more  than  500  cords  in  one  coaling ;  else  the  business 
would  be  profitable  neither  to  the  colliers  nor  to  the  master. 

Ashes,  and  their  component  parts,  are  of  too  little  consequence 
to  affect  the  price  of  wood ;  but  little  economy  can  be  observed  in 
relation  to  them. 

II.   Turfy  Peat. 

This  mineral  fuel  is  of  but  little  consequence  to  us,  because  there 
is  abundance  of  wood  and  stone  coal  in  the  country ;  nevertheless, 
we  will  give  it  a  cursory  notice  on  account  of  its  chemical  compo- 
sition, which,  to  iron  workers,  is  not  without  interest.  It  has  been 
found  that  turf  is  a  most  excellent  fuel  for  the  blacksmith's  forge, 
as  in  case-hardening,  tempering,  and  hardening  steel,  forging  horse 
shoes,  and  particularly  in  welding  gun  barrels.  For  this  purpose 
it  is  pressed  and  charred. 

Turf  is  generally  found  in  bogs,  in  horizontal  layers  from  ten  to 
thirty  feet  in  thickness :  sometimes  in  the  form  of  a  blackish-brown 
mud ;  sometimes  it  is  a  dark  peaty  mass,  and  often  a  combination 
of  roots  and  stalks  of  plants;  frequently  the  turf  layers  interchange 
with  layers  of  sand  or  clay.  Sea  water  is  better  adapted  to  the 
formation  of  turf  than  rain  or  spring  water. 

Turf  is  simply  dug  with  spades,  and  then  dried.  If  too  moist 
to  be  dug,  the  half  fluid  mass  is  piled  upon  a  dry  spot  and  there 
left  until  the  water  leaks  off,  and  until  the  mass  appears  dry  enough 
to  be  formed  into  square  lumps  in  the  form  of  bricks.  In  many  in- 
stances, however,  the  freshly  dug  turf  is  triturated  under  revolving 
edge  wheels,  faced  with  iron  plates  perforated  all  over  their  surface ; 
through  the  apertures  in  these  plates  the  turf  is  pressed  till  it  be- 
comes a  kind  of  pap ;  this  pap  is  put  into  a  hydraulic  press,  and 
squeezed  until  it  loses  the  greater  part  of  its  moisture.  It  is  then 
dried  and  charred  in  suitable  ovens.  The  charcoal  made  in  this 
way  deserves  the  notice  of  the  artisan. 


86  MANUFACTURE  OF  IRON. 

a.  Ashes. — The  amount  of  ashes  in  turf  varies  greatly;  and, 
economically  considered,  ashes   are   of  considerable  importance. 
Some  specimens  contain  only  one  per  cent.,  while  others  contain 
thirty  per  cent.,  which,  in  direct  proportion,  diminishes  the  value  of 
turf.     Eut  it  is  not  so  much  the  quantity  as  the  quality  of  these 
ashes  which  interests  us.     Their  value  as  a  fuel  to  the  blacksmith 
is  indicated  by  their  chemical  composition.     It  is  a  remarkable  fact 
that,  in  turf  ashes,  we  never  find  any  carbonated  minerals  ;  while 
they  contain  phosphates,  sulphates,  and  chlorides. 

An  analysis  of  turf  ashes  gave,  in  100  parts, 

Lime      -  15.25 

Alumina  20.5 

Oxide  of  iron  5.5 

Silex      -  41.0 

Phosphate  of  lime  -  15.0 

Chloride  of  sodium  15.5 

Sulphate  of  lime     -  21.0 

In  other  kind  of  turf,  thirty-four  per  cent,  of  phosphate  of  lime,  and 
six  per  cent,  of  chlorides,  were  found.  The  phosphates  and  chlorides 
have  an  excellent  influence  upon  the  hardening  and  welding  of  iron 
and  steel ;  and  if  we  use  turf  for  these  purposes,  we  should  analyti- 
cally investigate  the  composition  of  the  ashes  which  it  produces. 

Though  the  elements  of  turf  ashes  are  beneficial  to  the  working 
of  bar  iron  and  steel,  it  does  not  follow  that  they  are  equally  benefi- 
cial in  reducing  iron  ore;  for  in  the  blast  furnace  phosphates  of  any 
kind  are  injurious,  and  produce  a  cold-short  iron.  Therefore  we 
should  be  very  cautious  when  we  recommend  turf  for  the  blast  fur- 
nace. We  should  recommend  only  such  kinds  of  turf  as  contain 
neither  too  many  phosphates,  nor  too  great  an  amount  of  ashes ; 
otherwise,  we  run  the  risk  of  producing  bad  work  in  the  furnace. 
Dug  turf,  that  is  applicable  for  the  smelting  of  iron,  should  never 
contain  more  than  five  per  cent,  of  ashes. 

b.  Chemical  Analysis  of  Turf. — The  component  parts  of  turf 
differ  from  those  of  wood.     This  difference  is  owing  to  the  fact  of 
its  being  decomposed  woody  fibre.     We  present  an  analysis  of 
several  specimens : — 

One  hundred  parts  of  good  turf  contained,  besides  ashes, 

Garbon.  Hydrogen,  Oxygen. 

No.     I.          5T.03  5.63  31.T6 

No.    II.          58.09  6.93  31.3T 

No.  III.         57.79  6.11  30.77 


FUEL.  87 

We  find  here  less  oxygen,  but  more  combustible  matter,  than  in 
wood. 

c.  Practical  Remarks. — Turf  is  a  very  imperfect  fuel,  because  it 
generally  contains  too  much  foreign  matter ;  and  it  is  too  expensive 
where  wages  are  high.  A  great  deal  of  it  is  used  in  different  parts 
of  Europe,  where  cheap  labor  and  scarcity  of  wood  and  stone  coal 
render  it  more  available.  But  in  this  country,  there  are  few  places 
where  wood  and  stone  coal  cannot  be  had  at  reasonable  prices,  and 
as  yet  there  is  no  prospect  of  turf  coming  into  use  for  the  manufac- 
ture of  iron.  Still,  it  is  unquestionably  useful  in  working  steel  and 
bar  iron.  In  such  cases,  however,  it  should  be  subjected  to  a  che- 
mical analysis.  Turf  should  never  be  used  in  its  raw  form,  but 
only  when  charred.  Where  its  composition  is  shown  to  be  favorable 
by  chemical  analysis,  we  need  not  be  harassed  in  relation  to  its 
price,  for  its  utility  is  so  obvious  that  a  liberal  expenditure  may  be 
safely  hazarded.  The  expense  of  turf,  in  comparison  with  that  of 
wood  or  wood-charcoal,  may  be  estimated  by  weight.  The  specific 
gravity  of  a  cord  of  dry  wood  is  from  two  to  three  thousand  pounds; 
and,  if  we  consider  that  air-dried  wood  contains  from  thirty  to  forty 
per  cent,  of  water,  the  real  amount  of  combustible  matter  in  a  cord  is 
reduced  from  thirteen  hundred  to  two  thousand  pounds.  Air-dried 
turf  always  contains  more  or  less  water,  and  this  is  to  be  deducted 
before  we  can  know  its  real  value.  The  amount  of  water  varies 
exceedingly,  ranging  from  ten  to  forty  per  cent.  It  can  be  easily 
expelled  by  weighing  the  turf  when  green,  then  exposing  it  to  a 
boiling  heat  (212°),  and  again  weighing  it.  The  difference  is 
water.  According  to  this,  a  ton  of  air-dried  turf  ought  to  be  worth 
as  much  as  a  cord  of  wood,  provided  the  quantity  of  ashes  in  the 
turf  is  not  too  great,  say  ten  per  cent.  This  quantity  can  be  found 
by  weighing  a  piece  of  turf,  and  burning  it  slowly  on  a  plate  of 
sheet-iron,  until  all  the  carbon  is  expelled.  This  operation  requires 
a  red  heat.  The  remainder  is  ashes.  If  turf  is  dug  for  the  pur- 
pose of  charring,  it  is  advisable  to  employ  a  good  strong  turf-press. 
Turf,  thus  pressed,  chars  excellently,  and  yields  a  charcoal  as  hard 
again  as  the  best  sugar  maple,  or  hickory  coal. 

III.  Fossil  Coal. 

G.evlogy. — It  does  not  belong  to  our  department  to  treat  exten- 
sively of  the  geology  of  mineral  coal.  A  few  remarks  will  be  Suffi- 
cient to  explain  all  that  is  necessary  to  be  understood.  Fossil  coal 
may  be  conveniently  divided  into  three  distinct  classes :  The  upper, 


88  MANUFACTURE  OF  IRON. 

or  more  recent  geological  deposit,  is  called  brown  coal,  distinguished 
by  its  color,  which  is  mostly  brown,  and  its  texture,  which  is  that 
of  wood  slightly  charred.  It  occupies  the  same  geological  position 
as  fossiliferous  limestone,  above  chalk.  The  second  deposit  of 
mineral  coal,  generally  called  bituminous,  or  stone  coal,  is  below 
chalk.  This  coal  is  black,  more  or  less  of  a  vitreous  lustre.  The 
third  class  in  our  arrangement  is  anthracite  coal,  characterized 
by  its  great  hardness,  and  the  small  amount  of  hydrogen  it  evolves. 
Its  position  is  in  the  transition  or  volcanized  secondary  rocks.  All 
mineral  coal  varies  much  in  chemical  composition,  and  ranges  be- 
tween turf,  and  carbon  that  is  almost  pure. 

a.  Brown  Coal. — The  external  appearance  and  texture  of  brown 
coal  vary  as  much  as  its  chemical  composition.     Its  color  varies 
from  a  light  brown  to  a  deep  black.     Some  specimens  are  very 
friable ;  others  very  hard.     Its  structure  clearly  shows  it  to  be  the 
remains  of  a  vegetable  world ;  for  the  identical  woody  fibre,  the 
form  of  trunks  and  limbs  of  trees,  even  the  minutest  leaves  and 
fruit,  are  exhibited  with  striking  distinctness.    Coal  beds  resemble 
an  irregular  pile  of  trees,  limbs,  and  leaves.     The  powder  of  this 
coal  is  always  brown.     Sometimes  brown  coal  is  called  lignite, 
fossil  wood,  or  bituminous  wood — terms  which  are  not  sufficiently 
distinctive. 

b.  Water. — Brown  coal  generally  contains  a  large  amount  of 
water.     Some  specimens  contain  forty- three  per  cent.,  and  scarcely 
any  contain  less  than  twenty  per  cent.     Exposed  to  a  dry  atmo- 
sphere, brown  coal  is  very  apt  to  fall  into  slack,  and  lose  a  great  deal 
of  its  moisture;  but  it  never  becomes  entirely  dry.  It  is  thus  evident 
that  this  coal  constitutes  a  very  imperfect  fuel — inferior  even  to  turf, 

c.  Ashes. — The  amount  of  ashes  is  less  in  brown  coal  than  in 
turf,  and  varies  from   1.50  to  27.2  per  cent.,  as  in  Irish  coal. 
A  remarkable  difference  sometimes  exists  in  the  quantity  of  ashes 
yielded  by  the  same  piece  of  coal.     Brown  coal  is  very  seldom  of 
any  use  in  the  manufacture  of  iron,  partly  on  account  of  its  friability 
and  its  moisture,  but  more  particularly  on  account  of  the  composi- 
tion of  its  ashes.     Its  ashes  generally  abound  in  sulphates,  or  sul- 
phites, which  impart  sulphur  to  the  iron,  and  make  it  red-short.  We 
should,  therefore,  be  very  careful  in  the  use  of  this  coal  in  iron 
manufactories.     We  give  an  analysis  of  two  different  kinds  of 
brown  coal-ashes.     In  100  parts  of  ashes  there  were  found  : — 


FUEL.  89 

Sulphate  of  lime  3.6 

Sulphite  of  potash  -                                     1.9 

Sulphite  of  lime  -       25.4 

Sulphate  of  iron  -       50.0 

Sand  -       19.1 

Another  specimen  contained,  in  100  parts  of  ashes, 

Sulphate  of  lime                                    -  75.50 

Magnesia           -         -         -        -        -  2.58 

Alumina    -                  ....  11.57 

Oxide  of  iron    -                                   -  5.78 

Carbonate  of  potash  -                          -  2.64 

Sand                           -                          -  2.03 

The  amount  of  sulphur,  as  exhibited  by  these  analyses,  is  so  great 
that  it  is  dangerous  to  use  such  coal  in  the  manufacture  of  iron.  If 
the  quality  of  its  ashes  will  permit  its  use  in  the  manufacture  of 
alum,  it  may  be  considered  a  very  cheap  and  useful  article. 

d.  Chemical  Composition. — The  composition  of  the  combustible 
part  of  brown  coal  forms  the  connecting  link  between  turf  and 
bituminous  coal.     The  analysis  of  100  parts  of  this  coal  gives  us 
the  following  result : — 

Carbon.  Hydrogen.  Oxygen. 

Friable  brown,  I.        50.78  4.62  21.38 

"          «     II.        70.49  5.59  18.93 

Black  lignite,     I.         51.70  5.25  30.37 

"          «     II.        63.29  4.89  26.24 

The  residue  exhibits  the  amount  of  ashes.  Nitrogen  is  frequently 
found  in  this  species  of  coal,  but  it  seldom  amounts  to  1.50  per  cent. 

e.  Bituminous  Coal — Pit  Coal. — This  species  of  coal  possesses 
peculiar  interest,  because  of  the  immense  quantity  of  it  which  exists 
throughout  the  globe,  and  especially  in  our  own  country.     The 
Pittsburgh  coal  field,  consisting  entirely  of  this  coal,  is  superior  in 
magnitude  to  any  in  the  known  world.     Besides  the  coal  field  of 
Pittsburgh,  there  are  immense  coal  fields  in  Maryland,  Virginia, 
Alabama,  and  Illinois,  which  not  only  rival  the  largest  in  Europe, 
but  which  will  afford,  in  all  time  to  come,  an  inexhaustible  store  of 
fuel.     This  species  of  combustible  deserves  the  especial  attention 
of  the  iron  manufacturer.     Its  quality  is  generally  good,  its  appli- 
cation simple,  and  its  price,  beyond  comparison,  the  most  reasona- 
ble of  any  other  kind. 

To  extend  our  labor  to  the  highly  interesting  geological  investi- 


90 


MANUFACTURE   OF  IRON. 


gallons  which  have  exhausted  alike  the  light  of  science  and  the 
resources  of  art,  would  lead  us  too  far.  The  lover  of  such  re- 
searches will  find  ample  information  in  a  work  of  great  value 
(Statistics  of  Coal,  by  Richard  Cowling  Taylor,  Philadelphia,  lately 
published  by  J.  W.  Moore),  which  will  richly  repay  the  time  oc- 
cupied in  its  perusal.  Our  province  embraces  merely  a  description 
of  the  material,  and  of  its  component  parts. 

Bituminous  coal  is  characterized  by  its  dark  black  color,  and 
highly  vitreous  lustre.  Its  powder  is  black.  In  some  of  this  spe- 
cies, fibres  of  wood  resembling  soft  charcoal  may  be  distinctly  seen. 
Some  specimens  contain  more  or  less  sulphur  in  the  form  of  the 
yellow  sulphuret  of  iron,  visible  by  the  naked  eye.  This  is  a 
mechanical  admixture.  If  the  quantity  of  this  sulphuret  is  very 
large,  the  coal  is  unfit  for  the  manufacture  of  iron.  This  coal 
is  mostly  stratified  parallel  with  the  direction  of  the  vein,  and 
breaks  into  square,  almost  cubical  pieces. 

/.  Water. — Good  pit  coal  contains  very  little  water  in  admix- 
ture. Its  close  texture  and  its  resinous  character  prevent  the 
penetration  of  air  or  water.  But  if  the  coal  is  very  friable,  which 
is  frequently  the  case  with  the  external  portion  of  the  veins,  water 
may  exist  in  the  crevices ;  but  in  amount  so  small  as  scarcely  to 
injure  the  quality  of  the  coal. 

g.  Ashes. — This  article  deserves  considerable  attention,  on  ac- 
count of  its  influence  in  the  blast  furnace.  The  ashes  of  bitumi- 
nous coal  are  generally  composed  of  silex  and  alumina ;  seldom  of 
lime,  magnesia,  or  any  other  base ;  and  for  this  reason  possess 
much  interest.  The  amount  of  ashes  in  this  coal  varies  from  one 
to  twenty-five  per  cent. ;  coal  which  contains  more  than  five  per 
cent,  of  ashes  should  scarcely  be  used  in  the  blast  furnace.  If 
any  is  used  which  contains  a  greater  per  centage  than  that,  the 
furnace  will  not  work  well,  and  a  great  loss  of  iron,  or  the  produc- 
tion of  bad  iron,  is  the  consequence.  Even  in  puddling  furnaces, 
a  large  amount  of  ashes  is  injurious,  as  we  shall  hereafter  see. 

For  the  sake  of  comparison,  we  give  two  analyses  of  ashes  from 
this  species  of  coal : — 

Ashes  from  a  species  of  French  seal 
yielded  of 

Sulphate  of  lime  -        -  80.8 

Lame      -  «•  3.S 

Silex  -  14.2 

Oxide  of  iron  -        -  1.7 


White  agfoes  of  American  coal  yielded 
of 

S0ex      - 

Lime 

Alumina 


85.7 
2.5 

8.2 


Sulphate  of  lime 


3.6 


FUEL.  '  91 

We  here  observe  the  great  preponderance  of  the  electro-negative 
over  the  electro-positive  elements.  How  far  this  circumstance  in- 
terferes with  the  manufacture  of  iron  will  be  investigated  under  the 
heads  of  the  theory  of  the  blast  furnace,  and  the  philosophy  of 
manufacturing  wrought  iron. 

Chemical  Composition.— ;The  chemical  composition  of  the  com- 
bustible parts  of  bituminous  coal  ranges  between  that  of  brown 
coal  and  anthracite.  An  analysis  of  100  parts  of  this  coal  exhibit- 
ed the  following  result : — 

Splint  coal.  Cannel  coal.  Glance  coal. 

Carbon       70.9       Carbon       72.22       Carbon      90.10 
Hydrogen    4.3       Hydrogen     3.93        Hydrogen    1.3 
Oxygen      24.8       Oxygen      21.05       Oxygen       6.5 

This  coal  generally  contains  from  1  to  1.5  per  cent,  of  nitrogen ; 
"which,  however,  for  our  purpose,  is  of  no  consequence. 

The  above  table  shows  that  the  quantity  of  hydrogen  and  oxy- 
gen is  less  than  that  in  woody  fibre,  turf,  and  brown  coal,  a  circum- 
stance worthy  of  notice.  We  shall  refer  again  to  this  subject  when 
we  come  to  speak  of  the  article  anthracite. 

h.  Practical  Remarks. — Much  that  is  highly  interesting  might 
be  said  concerning  this  article,  but  we  are  forced  to  condense  our 
observations  as  closely  as  possible.  The  thickness  of  the  coal  seams, 
as  distributed  in  the  stratified  coal  measures,  varies  from  an  inch 
to  sixty  feet.  Veins  less  than  two  feet  thick  are  hardly  worth  work- 
ing. High  wages  would  absorb  nearly  all  the  profit  derived  from 
working  them ;  besides,  such  veins  seldom  afford  as  good  a  quality 
of  coal  as  is  needed  for  the  manufacture  of  iron.  These  veins  are 
generally  slaty  and  sulphurous,  and,  except  in  cases  of  necessity, 
should  be  rejected.  Veins  more  than  two  feet  thick  are  generally 
of  better  quality,  as  well  as  more  workable.  In  fact,  coal  three 
feet  thick  can  be  raised  at  very  nearly  the  same  cost  as  veins  of 
greater  thickness.  In  an  economical  point  of  view,  therefore,  a 
thick  vein  presents  but  little  advantage. 

i.  Classification. — Geologists  have  classified  this  coal  from  its  ex- 
ternal appearance,  without  any  relation  to  its  chemical  composition. 
The  English  coal-diggers  distinguish  four  kinds,  to  wit:  1,  cubical 
coal ;  2,  slate  or  splint  coal ;  3,  cannel  co^l ;  and  4^  glance  coal. 
Whether  this  classification  is  a  correct  o&e,  we  will  not  venture  to 
say ;  for  our  purpose,  at  least,  it  has  no  specific  use.  The  only  exact 
basis  of  classification  is  that  of  chemical  composition.  But  for  the 
sake  of  usage  we  will  adopt  the  classification  commonly  presented. 


92  MANUFACTURE   OF  IRON. 

1.  Cubical  Coal — Pittsburgh  seam — is  black,  shining,  compact, 
and  tolerably  hard.     It  comes  from  the  mines  in  almost  cubical 
masses.     The  general  direction  of  the  vein  is  that  of  the  cleavage. 
This  coal  cakes  with  facility,  and  on  that  account  is  valuable  to  the 
blacksmith,  for  it  forms  very  readily  a  wall  and  vault  around  his 
fire.  t 

2.  Slate,  or  Splint  Coal,  seam  next  above  the  Pittsburgh,  is  of  a 
dull  black  color,  very  compact,  harder  than  cubical  coal,  and  mined 
with  greater  difficulty.     It  splits  very  readily,  like  slate,  but  resists 
cross  fracture ;  it  separates  in  large,  square-edged  masses,  and  burns 
without  coking.     It  is  somewhat  heavier  than  cubical  coal,  and 
frequently  yields  a  considerable  bulk  of  white  ashes.     Where  it 
does  not  contain  too  much  ashes,  it  is  an  excellent  fuel  for  the 
blast  furnace. 

3.  Cannel  Coal  generally  lies  in  seams  below  the  Pittsburgh 
vein.    Its  color  is  between  velvet  and  grayish-black ;  it  has  a  resin- 
ous lustre.     It  is  as  hard  as  splint  coal,  kindles  like  pitch,  and 
burns  with  a  white  bright  flame.     This  coal  works  very  clean  in 
the  mine,  and  scarcely  soils  the  fingers  when  rubbed.     It  is  found 
in  Ohio  and  Missouri. 

4.  Grlance  Coal  very  closely  resembles  anthracite,  and  is  of  an 
iron  black  color.     Occasionally  it  exhibits  an  iridescence  somewhat 
resembling  that  of  tempered  steel.     It  has  a  beautiful  metallic  lus- 
tre, does  not  soil,  and  its  fragments  are  sharply  edged.     It  forms 
coke  with  difficulty. 

The  classification  just  presented  is  unquestionably  a  very  imper- 
fect one,  because  it  furnishes  us  with  no  marks  by  which  the  differ- 
ent classes  are  distinctly  indicated.  This  is  evident  from  the  fact 
that  the  same  vein  not  unfrequently  contains  all  the  varieties  in- 
cluded in  these  classes.  A  correct  classification  would  include  all 
bituminous  coal,  so  called  from  its  resinous  aggregation,  and  the 
amount  of  hydrogen  it  contains.  This  class  may  very  easily  be 
distinguished  by  its  property  of  forming  coke ;  for  wood,  turf,  brown 
coal,  and  anthracite  do  not  yield  this  article. 

Jc.  Mining  of  Coal. — Where  coal  fields  are  situated  above  the 
water  level,  and  with  the  advantage  of  ascent,  the  working  of  coal 
is  comparatively  easy.  The  pit  water  flows  off  by  itself,  and  there 
is  but  little  trouble  in  ventilation.  In  such  cases,  all  that  is  required 
is,  to  open  a  drift,  to  timber  it  well  at  the  mouth,  and  to  make  such 
arrangements  in  train  or  plank  roads  as  will  afford  a  quick  and  easy 
hauling.  A  very  cheap  and  useful  arrangement  is  that  of  the 
Pittsburgh  coal-diggers.  A  two  wheel  cart,  of  about  twelve  bushels 


FUEL.  93 

capacity,  is  pushed  on  a  plank  track  by  a  man,  assisted  by  a  strong 
dog,  "which  runs  before  the  cart.  We  have  never  found  much  ad- 
vantage in  a  large,  high,  and  wide  drift  or  level.  We  have  paid 
quite  as  high  a  price  for  hauling  by  horses  or  mules  on  an  iron  tram- 
road,  as  that  paid  for  the  use  of  the  above-mentioned  cart.  Where 
a  coal  mine  is  very  extensive,  or  where  the  wagons  have  to  be  pulled 
up  an  ascent,  a  wide  track,  and  horses  and  mules,  may  be  advan- 
tageous ;  but,  considering  the  cost  of  a  spacious  drift,  rails,  wagons, 
&c.,  very  little  is  gained  in  expensive  improvements.  A  plank  track 
is  easily  removed ;  it  may  be  turned  in  any  direction,  even  to  the 
very  face  of  the  work-rooms,  and  will  last  a  long  time,  if  constructed 
of  good  white  oak.  We  have  paid  twenty  cents  for  hauling  one 
hundred  bushels  from  the  room  to  the  mouth  of  the  pit,  and  tole- 
rable wages  were  hardly  made  at  that ;  while  an  equal  amount 
readily  pays  reasonable  wages,  if  the  above-mentioned  hand-cart  or 
dog-cart  is  employed.  If  locality,  or  other  circumstance,  does  not 
permit  an  opening  or  drift  according  to  the  inclination  of  the  coal, 
it  is  necessary  to  drive  a  dead  level  in  the  coal  to  drain  the  mine  of 
water  ;  and  in  case  this  cannot  be  done,  a  dead  level  below  the  coal 
must  be  drifted  until  the  coal  is  reached.  This  is  illustrated  by  the 
following  diagram :  a,  #,  c,  d,  e,  f  represent  coal  veins,  and  g,  a 

Fig.  19. 


Draining  level. 

dead  or  water-draining  level,  which,  of  course,  can  be  used  as  a  win- 
ning level.  The  shaft  h  may  be  used  as  a  ventilator  of  the  pit,  or 
both  ventilator  and  winning  shaft. 

Coal  veins,  situated  above  the  water  level  of  the  country,  may  be 


94  MANUFACTURE    OF  IRON. 

worked  at  but  little  expense,  that  is,  require  no  immediate  capital ; 
but  if  they  are  situated  below  the  water  level,  more  attention  and 
greater  means  are  required.  If  the  coal  is  so  low  that  a  mine  can- 
not be  drained  by  a  level,  machinery,  either  water-wheels  or  steam- 
engines,  as  well  as  pumps  to  raise  the  water  sufficiently  high  to  permit 
its  flow  into  the  nearest  river,  must  be  resorted  to.  In  such  cases, 
vertical  shafts  are  in  common  use.  Such  a  shaft  is  constructed  of 
timber,  walled  with  stones  or  bricks,  or  of  iron  cylinders.  Its  dimen- 
sions depend  entirely  on  the  amount  of  coal  required  to  be  hoisted. 
If  the  section  of  such  a  pit,  or  shaft,  is  round,  it  should  never  be 
less  than  ten  feet  in  diameter :  it  may  increase  thence  to  twenty  feet. 
Such  a  shaft  must  be  divided  into  different  compartments,  one  of 
which  should  be  always  reserved  for  pumps  and  water-pipes.  The 
following  diagrams  represent  its  various  forms :  a,  a  are  designed 

Fig.  20.  Fig.  21.  Fig.  22. 


Sections  of  shafts. 

for  the  pumps.  If  this  shaft  is  made  of  a  square,  instead  of  a  round 
form,  it  should  not  be  less  than  eight  by  ten,  or  ten  by  twelve  feet 
for  a  double  pit.  Where  the  coal  is  not  too  far  below  the  surface,  say 
fifty  or  one  hundred  feet,  inclined  planes  may,  in  some  instances, 
be  preferable  to  vertical  pits.  In  such  a  case,  the  section  may  be 
smaller,  and  the  same  railroad  cars  that  are  used  above  ground  may 
be  used  below  ground.  But  whatever  plan  is  adopted,  the  shaft 
should  be  sunk  to  the  lowest  point  of  the  coal  vein.  The  working 
of  coal  by  means  of  a  shaft  is,  in  fact,  not  more  expensive  than  that 
of  more  highly  located  veins.  It  is  attended  with  some  disadvan- 
tages to  the  workmen  ;  these  are  generally  balanced  by  a  good  roof. 
But  the  expense  of  shaft  ventilation,  engine,  and  pumps  falls  heavily 
on  the  proprietor;  this  once  met,  the  work  may  be  prosecuted  cheaply 
and  with  facility.  A  good  circulation  of  fresh  air  is  effected  only 
at  great  expense, and  with  considerable  difficulty;  this  circumstance 
needs  great  attention  in  extensive  coal  mines.  There  is  no  reason, 
at  the  present  time,  why  iron  masters  should  go  to  a  great  depth  for 


FUEL.  95 

coal.     Coal  above  the  water  level  is  so  abundant  that  any  farther 
consideration  of  deep  coal  pits  would  be  superfluous. 

The  mode  of  working  a  coal  vein  depends  on  several  circum- 
stances :  partly  on  the  roof,  upon  the  kind  of  coal,  whether  for 
our  own  use  or  for  the  market,  and  upon  the  thickness  of  the  vein. 
The  following  are  the  methods  practiced  : — 

1.  Working  with  pillars  and  rooms,  where  the  pillars  left  bear 
precisely  that  proportion  to  the  coal  excavated  which  is  required 
to  support  the  incumbent  strata  or  roof.     These  pillars  are  gene- 
rally lost. 

2.  Working  with  post  and  stall.     Here  the  pillars  left  are  of  a 
larger  size  than  usual,  and  stronger  than  is  requisite  for  supporting 
the  superior  strata.    These  are  so  constructed  that  they  may  be  re- 
moved whenever  the  regular  work  is  done.     This  method  of  work- 
ing is  best  adapted  for  coal  veins  more  than  three  or  four  feet  thick. 

3.  Working  with  post  and  stall,  or  with  comparatively  small 
rooms.     By  this  method,  an  unusually  large  proportion  of  coal  is 
left,  with  a  view  of  working  backward  towards  the  starting-point, 
whenever  the  coal  field  is  worked  to  the  whole  extent ;  then  by 
taking  away  every  pillar  completely,  if  possible,  the  roof  is  per- 
mitted to  fall  in,  following  the  miners  as  they  retreat. 

4.  Taking  out  all  the  coal,  and  leaving  no  pillars  at  all.     By 
this  plan,  the  roof  falls  in  as  the  diggers  retire. 

The  first  two  methods  are  practiced  for  the  thicker  coal  seams. 
Where  the  veins  are  thicker  than  three  feet,  the  two  latter  methods 
are  dangerous  and  expensive.  Where  the  coal,  roof,  and  pavement 
are  of  equal  hardness,  the  first  and  second  methods  will  answer;  but 
where  the  pavement  is  soft,  the  pillars  should  be  uncommonly  strong 
to  prevent  the  sinking  of  the  coal.  They  should  be  equally  strong 
where  the  coal  is  soft,  for  otherwise  they  would  be  crushed,  and 
the  coal  lost.  The  same  principle  may  be  extended  to  a  roof  that 
is  soft  and  brittle. 

Bearing  all  these  circumstances  in  mind,  it  may  be  stated,  gene- 
rally, that,  where  the  coal,  roof,  and  pavement  are  strong,  all  the 
above  methods  may  answer ;  but  where  they  are  soft,  strong  pillars 
and  rooms  of  moderate  size  are  required :  in  this  way,  when  the 
miners  retreat  to  the  starting-point,  the  greater  part  of  the  coal 
may  be  got  out. 

The  proportion  of  coal  taken  out  to  that  left  in  the  pillars,  when 
it  is  our  intention  to  remove  all  the  coal  at  the  first  working  varies 

O" 

from  four-fifths  to  two-thirds.  A  loss  even  of  that  amount  throughout 


96 


MANUFACTURE   OF   IRON. 


the  whole  area  of  the  coal  field,  ought  to  be  prevented.  If  no  acci- 
dents happen,  this  can  be  done  by  adopting  the  third  plan. 

When  a  coal  field  is  opened,  and  a  systematical  method  of  working 
is  resolved  upon,  we  should  divide  the  coal  field  into  square  spaces, 
where  pillars,  rooms,  and  roads  are  properly  laid  out.  In  accordance 
with  this  plan  must  the  air  pits  be  situated,  and  a  system  of  venti- 
lation arranged  which  will  secure  both  the  safety  of  the  working  men, 
and  the  progress  of  the  operation.  Where  the  coal  is  soft  and  friable, 
particularly  where  it  is  slaty  and  sulphurous,  perfect  ventilation  is 
indispensable.  Hard,  clean  coal  is  not  so  dangerous,  and  requires, 
therefore,  less  care.  Coal  pits  ought  to  be  opened  in  summer,  and 
continued  during  winter ;  an  air  shaft  should  be  driven  during  the 
winter,  that  a  progressive  work  for  the  warm  season  may  be  secured. 

If  the  coal  stands  edgewise,  or  nearly  perpendicular,  the  thickest 
stratum  of  rock  is  the  best  place  for  driving  a  shaft.  The  pit  should 
be  strongly  timbered  or  walled,  to  prevent  its  being  crushed.  When- 
ever the  shaft  has  its  proper  depth,  galleries  must  be  driven  across 
all  the  coal  strata,  as  shown  in  Fig.  23.  These  galleries  can  be 

Fig.  23. 


Opening  of  galleries. 


multiplied  for  the  greater  convenience  of  the  winning.     All  the 
coal  is  then  taken  out  at  the  working  shaft  c. 

For  lifting  coal  in  a  shaft,  chains  or  ropes  are  used ;  the  former 
are  dangerous,  and  often  unexpectedly  break.     Hemp  ropes  are 


FUEL.  97 

more  safe,  but  they  are  expensive.  We  doubt  whether  wire  ropes 
will  answer  the  purpose ;  for,  besides  the  friction  of  coal,  sand,  and 
mud,  the  pit  water  is  very  destructive.  For  these  reasons,  hemp 
or  inanilla  ropes  are  probably  the  cheapest  as  well  as  the  best. 

If  coal  veins  are  not  horizontal  or  vertical,  the  best  plan  is  to 
follow  with  the  shaft  the  dipping  of  the  coal,  and  hoist  on  an  in- 
clined plane.  All  the  other  arrangements,  as  pumps,  &c.,  should 
be  constructed  in  accordance  with  this  principle. 

The  price  of  digging  coal  varies  much.  In  Frostburg,  Maryland, 
a  ton  of  coal  is  dug  in  the  thick  or  twelve  feet  vein  at  twenty-five 
cents;  in  thinner  veins,  in  the  same  region,  at  from  fifty  to  seventy- 
five  cents ;  sometimes  as  high  even  as  a  dollar  is  paid  for  a  ton  of 
twenty-three  bushels.  In  the  Pittsburgh  vein,  the  price  varies  from 
one  cent  and  a  half  to  two  cents  per  bushel,  and  a  vein  of  the  same 
thickness,  twelve  feet,  can  be  dug  in  the  counties  of  Armstrong  and 
Westmoreland,  Indiana,  at  one  cent  a  bushel.  Great  difference  in 
the  price  is  occasioned  by  the  difference  in  the  quality  of  coal — 
whether  it  is  designed  for  our  own,  or  for  market  use.  If  the  coal  is 
to  be  screened,  and  the  slack  removed,  workmen  demand,  and  of 
course  deserve,  higher  wages,  than  when  mixed  coal  and  slack  are 
received.  Wages  also  depend,  in  a  great  measure,  on  the  quality, 
softness  or  hardness  of  coal,  upon  the  thickness  of  the  vein,  and  upon 
the  roof  and  pavement.  Workmen  may  make  good  wages  at  one 
cent  a  bushel  in  one  place,  and  poor  wages  at  five  cents  a  bushel  in 
another  place.  As  a  general  rule,  a  six  feet  vein,  with  a  strong,  hard 
roof  and  pavement,  and  a  strong  coal,  with  soft  undermining,  is, 
of  all  others,  the  most  favorable.  The  hauling  of  coal  from  the 
work  rooms  to  the  mouth  of  the  pits  is  a  matter  of  great  import- 
ance, for  imperfect  roads,  wagons,  water,  &c.,  bear  heavily  upon 
the  transportation  of  coal.  In  one  case,  ten  cents  a  ton  may  be 
ample  remuneration ;  while,  in  another  case,  respectable  wages 
cannot  be  made  at  thirty  cents  a  ton.  Sometimes  one  set  of  hands 
contract  both  for  hauling  and  digging.  This  is  a  good  arrange- 
ment ;  but,  where  the  coal  mines  are  extensive,  it  is  not  practicable. 

The  most  prevailing  method  of  valuing  coal,  as  well  in  trade  as 
in  digging,  is  by  measurement.  Any  intelligent  man  must  be  con- 
vinced that  this  is  a  very  imperfect  method  of  valuation.  The  value 
of  coal  can  be  deduced  from  its  specific  gravity  alone  ;  and  there- 
fore depends  upon  its  absolute  weight.  A  proper  deduction  must  of 
course  be  made  for  the  ashes  it  contains.  The  specific  gravity  of 
coal  varies,  sometimes  in  the  same  vein,  from  1.2  to  1.9 — a  differ- 
7 


98  MANUFACTURE    OF  IRON. 

ence  of  thirty  per  cent.  That  is  to  say,  a  given  quantity  of  coal 
may  furnish  just  thirty  per  cent,  more  combustible  matter  than  ano- 
ther equal  quantity  in  the  same  vein.  Sooner  or  later,  measurement 
by  weight  will  be  generally  introduced  in  the  coal  trade.  This  will 
benefit  the  producer  no  less  than  the  consumer.  Whether  a  ton  is 
assumed  to  be  2000  pounds,  or  2240  pounds  ;  whether  this  or  that 
standard  of  measurement  by  weight  be  adopted,  it  is  certain  that 
uniformity  of  estimation  would  soon  settle  the  real  value  of  coal. 
In  our  case,  this  method  would  be  even  of  more  consequence  than 
to  the  public  and  the  trade  generally.  In  England,  coal  is  sold  by 
the  chaldron;  in  Germany  and  France,  by  weight;  in  the  United 
States,  by  almost  every  variety  of  weight  and  measure.  For  what 
reason  is  coal  sold  in  Boston  and  New  York  by  the  ton,  chaldron, 
and  bushel  ?  Why  is  anthracite  sold  in  Baltimore  by  the  ton,  and 
bituminous  coal  all  over  the  West  by  the  bushel  ?  The  State  of 
Pennsylvania  charges  toll  by  the  1000  pounds  on  its  own  works ; 
while  the  workmen  dig  mostly  by  measure,  and  the  proprietors  sell 
either  by  the  ton  or  bushel.  How  complicated  and  troublesome  is 
such  an  arrangement !  Some  of  the  Eastern  States  recognize  a 
ton  of  coal  as  2000  pounds ;  others  as  2240.  Nova  Scotia  coal  is 
sold  at  Boston  by  the  chaldron.  Some  estimate  the  chaldron  at 
2928,  and  others  at  3000  pounds.  In  New  York,  a  ton  is  esti- 
mated at  2000. pounds;  in  Philadelphia,  at  2240;  while  in  Pitts- 
burgh, coal  is  sold  by  the  bushel.  All  United  States  customs  are 
regulated  at  2240  pounds. 

The  absurdity  of  buying  by  measure  will  appear  still  more  ob- 
vious, if  we  consider  that  coal  assumes  a  greater  bulk  when  it 
falls  into  slack,  than  when  in  coarse  lumps ;  and  that  wet  coal  is 
not  so  heavy  as  dry  coal.  A  bushel  of  dry  coal,  for  instance,  will 
weigh  eighty-five  pounds ;  but  the  same  coal,  when  wet,  will  weigh 
only  eighty  pounds.  This  difference  increases  when  coal  is  slaty 
and  brittle.  The  buyer  is  the  one  who  suffers  most  by  measure- 
ment. It  may  be  said  that  three  bushels  of  coarse  coal  make  four 
bushels  of  small  coal,  and,  when  wetted,  five  bushels. 

The  only  reason  which  may  be  assigned  for  the  existence  of  this 
absurd  habit  of  measuring  coal,  is  the  trouble  which  the  erecting 
and  controlling  of  scales  occasion  ;  but  this  difficulty  may  be  effec- 
tually obviated,  if  self-registering  scales  are  placed  at  the  mouth 
of  the  coal  pit,  or  at  any  convenient  place. 

The  amount  of  bituminous  coal  throughout  the  United  States  is 


FUEL.  99 

immense.  We  shall  speak  of  this  subject  under  the  following  ar- 
ticle : — 

I.  Anthracite. — The  application  of  this  mineral  fuel  to  the  manu- 
facture of  iron  is  of  very  recent  date.  After  many  unsuccessful 
trials  and  difficulties,  which  at  one  time  seemed  insurmountable, 
Pennsylvania  enterprise  and  perseverance  were  crowned  with  suc- 
cess. Prof.  W.  R.  Johnson,  in  his  "Notes  on  the  Use  of  Anthra- 
cite in  the  Manufacture  of  Iron,"  gives  a  very  interesting  account 
of  these  difficulties,  and  of  the  success  with  which  anthracite  has 
been  applied  in  the  blast  furnace. 

Water. — Anthracite  is  too  compact  and  hard  to  absorb  water, 
or  to  contain  it  in  admixture. 

Ashes. — The  amount  of  ashes  is  often  very  considerable,  varying 
from  one  to  thirty  per  cent.  Their  chemical  composition  is  princi- 
pally silex,  with  but  little  alumina,  and  sometimes  oxide  of  iron. 

Chemical  Composition. — The  composition  of  anthracite  resem- 
bles very  closely  that  of  charcoal  and  coke.  Hydrogen  and  oxygen, 
gradually  diminishing,  amount,  in  the  most  perfect  specimens,  to 
scarcely  anything.  We  present  an  analysis  of  anthracite  : — 

Pennsylvania.  South  Wales.  Massachusetts  (Worcester). 

Carbon        94.89           Carbon        94.05           Carbon  28.35 

Hydrogen     2.55           Hydrogen     3.38           Hydrogen  0.92 

Oxygen         2.56           Oxygen         2.5T           Oxygen  2.15 

Ashes  68.65 

Practical  Remarks. — Anthracite  which  contains  more  than  five 
per  cent,  of  ashes  is  of  no  use  in  the  blast  furnace,  and  of  but  little 
use  in  the  puddling  and  re-heating  furnaces.  But  good  anthracite 
is  undoubtedly  the  most  perfect  of  all  fuels  for  the  manufacture  of 
iron.  Its  application  is  simple;  its  hardness  prevents  it  from  falling 
into  slack ;  and  the  small  amount  of  hydrogen  it  contains  makes  it 
advantageous  for  the  blast  furnace  operation.  By  proper  applica- 
tion, anthracite  will  supersede,  in  economy,  bituminous  coal.  The 
mining  operations  of  anthracite  are  more  simple  than  those  of  bitu- 
minous coal.  Less  danger  is  to  be  apprehended  from  the  effect  of 
bad  air  or  coal-damp ;  therefore  less  expenditure  for  ventilation,  as 
well  as  for  pavement,  roof,  and  coal.  It  is  so  hard  that  the  last 
remains  of  coal  can  be  removed.  A  ton  of  anthracite,  of  2240 
pounds,  sells  at  present,  in  Philadelphia,  at  from  three  dollars 
and  eighty-five  cents  to  four  dollars ;  in  New  York,  at  from  five 


100  MANUFACTURE    OF   IRON. 

dollars  and  fifty  cents  to  six  dollars ;  and  in  Boston,  at  from  six 
dollars  and  fifty  cents  to  seven  dollars.  These  are  market  prices, 
on  which  large  manufacturers  generally  receive  a  discount  of  from 
five  to  ten  per  cent. 

m.  G-eneral  Remarks  on  Fuel. — Wood  is  at  present  so  abundant 
throughout  the  United  States,  that  charcoal  furnaces  and  forges  may 
Tbe  carried  on  for  a  great  length  of  time,  without  apparently  dimi- 
nishing its  quantity;  still,  so  rapidly  are  civilization  and  wealth  pro- 
gressing, so  rapidly  is  the  consumption  of  iron  augmenting,  that 
our  attention  cannot  be  otherwise  than  forcibly  turned  to  mineral 
fuel  as  a  substitute  for  wood  in  the  manufacture  of  iron.  Peat  or 
turf  is  not  sufficiently  distributed  to  deserve  any  attention.  There 
are  peat  bogs  in  the  States  of  New  York,  Michigan,  Rhode  Island, 
New  Hampshire,  and  Maine,  and  possibly  in  other  States;  but  its 
application  in  our  country  is  so  limited,  and  will  probably,  for  some 
time  to  come,  be  so  limited,  that  it  hardly  deserves  our  notice.  In 
France,  Germany,  Bohemia,  and  Russia,  peat  is  used  for  the  manu- 
facture of  iron;  but  here,  independent  of  any  other  cause,  the 
price  of  turf  would  prevent  its  application  for  this  purpose.  In 
countries  where  no  mineral  coal  exists,  its  application  may  be  ad- 
vantageous. The  reasons  we  have  given  against  the  use  of  turf 
apply  equally  well  against  the  use  of  brown  coal.  Some  kinds  of 
lignite  constitute  a  good  fuel  in  the  puddling  furnace,  as  well  as  in 
re-heating  and  sheet  ovens;  but  their  application  in  the  blastfurnace 
is  very  limited.  Lignites  found  in  the  United  States  are  very  pro- 
perly used  only  for  the  manufacture  of  alum  and  copperas. 

n.  Of  all  the  coal  deposits,  those  of  anthracite  and  bituminous 
character  deserve  our  closest  attention.  Their  utility  in  the  manu- 
facture of  iron,  and  their  extraordinary  magnitude  throughout  the 
United  States,  give  to  the  iron  business  of  this  country  prospects  the 
most  flattering  of  those  of  any  nation,  or  of  any  time.  England 
was  supposed  to  include,  until  recently,  the  great  coal  deposits  -of 
the  world;  but  these  shrink  into  insignificance  when  compared 
with  the  gigantic  deposits  of  the  United  States.  The  amount  of 
coal  distributed  throughout  the  world  is  as  follows : — 

United  States  of  America  -     133,132  square  miles. 

Anthracite  of  Pennsylvania  437      "          " 

British  America  -  18,000      "          " 

Great  Britain       -  8,139      "          " 

u  and  Ireland  (anthracite)  3,720      "          " 


FUEL. 


101 


3,408  square  miles. 
1,719      "        " 
518      "        " 


Spain 

France 

Belgium 

How  great  the  prospect,  how  extensive  and  durable  the  basis  of 
comfort,  prosperity,  and  happiness,  to  the  citizens  of  the  United 
States,  this  immense  wealth  of  mineral  fuel  discloses  !  The  dis- 
tribution of  coal  throughout  the  different  States  of  the  Union  is  as 
follows : — 

Alabama   -  3,400  square  miles. 

Georgia      -  150      "         " 

Tennessee  4,300      "         " 

Kentucky-  13,500      "         « 

Virginia    -  21,195      " 

Maryland-  550      "         " 

Ohio  11,900      "         " 

Indiana     -  7,700      "         " 

Illinois       -  44,000  (?) "         " 

Pennsylvania     -  15,437      "         " 

Michigan 5,000      "         " 

Missouri    -  -          6,000      "         " 

By  this  table,  we  find  that  England,  Ireland,  Scotland,  and  Wales 
united,  do  not  contain  so  much  coal  as  the  State  of  Ohio.  We  have 
omitted,  in  the  above  estimate,  the  smaller  coal  tracts  in  different 
States,  as  not  worth  mentioning. 

United  States  Goal  Measurement. — 

Ordinary  estimate  of  bituminous  coal:  28  bushels  =  1  ton  at  2240  Ibs. 
At  some  places,  30      "       "  " 

We  also  find  it  stated  at  26J    "       "  " 

At  Richmond,  Virginia,  coal  pits,  a  bushel  =  5  pecks  =  90  Ibs. 
The  same  coal  on  board  a  vessel  "       =4      "      =72    " 

In  the  South,  bituminous  coal  is  sold  by  the  barrel,  weighing 
172|  =  13  barrels  =  1  ton. 

In  New  York,  as  well  as  in  Boston,  and  elsewhere  in  the  East, 
a  ton  of  coal  =  2000  ii>s. 

On  the  State  Canal  u  d  Tidewater  Canal,  Pa.,  toll  is  levied  at 
1000  Ibs. 

In  Pennsylvania,  Ohio,  and  several  other  States,  a  bushel  =  80 
Ibs.  of  coal. 

Nova  Scotia  coal  is  sold  by  the  chaldron  =  3360  Ibs.,  or  42 
bushels. 

In  Boston,  the  retail  chaldron  is  but  2500  or  2700  Ibs. 


102  MANUFACTURE   OF  IRON. 

Prices  of  coal  at  the  coal  pits : — 

In  France  -                          -  $1  50  to  $3  50  per  ton. 

«  Germany  1  75  «     2  50    «     « 

"  England  1  50  "     2  50    «     " 

"  Pennsylvania  (anthracite)  2  00  "     2  25    "     " 

"  Pittsburgh  (bituminous)   -  50  "     1  00    "     " 

IV.  Distillation  of  Fuel. 

If  raw  fuel  is  inclosed,  with  exclusion  of  atmospheric  air,  in  an 
iron  or  any  other  retort,  and  if  to  this  fuel  we  apply  heat,  a  decompo- 
sition ensues,  and  the  result  of  such  decomposition  varies  accord- 
ing to  the  kind  of  matter  with  which  the  retort  was  charged.  From 
the  moment  heat  is  applied,  the  elements  of  the  matter  separate, 
and,  according  to  the  temperature,  form  new  compounds,  which 
did  not  previously  exist  in  the  raw  material.  If  we  charge  the  retort 
with  wood,  the  first  compound  which  escapes  is  water ;  this  existed 
in  the  wood  either  in  the  form  of  sap,  that  is,  water  combined  with 
soluble  matter,  or  as  hygroscopic  water,  attracted  and  retained  by 
the  porous  aggregation  of  the  wood.  Hydrogen  and  oxygen  are 
then  expelled,  and  form  chiefly  water,  and  partly  other  composi- 
tions. A  small  amount  of  oxygen  and  hydrogen  is  left,  to  form,  by 
an  increasing  temperature,  different  compounds  with  carbon.  Hy- 
drogen combines  with  a  small  amount  of  carbon,  to  form  carburetted 
hydrogen  (the  fire-damp  of  the  coal  pits) ;  after  that,  a  mixture  of 
a  great  many  compounds,  consisting  of  carburetted  hydrogen,  tar, 
acetic  acid,  messit,  or  wood  alcohol,  creasote,  naphtha,  &c.,  is  dis- 
tilled, which  can  be  condensed  from  its  gaseous  into  a  liquid  state, 
by  introducing  it  into  a  cold  receiver.  The  same  law  which  governs 
the  distillation  of  wood,  is  applied  to  the  distillation  of  turf,  brown 
coal,  bituminous  coal,  &c.,  with  this  difference  in  the  product,  that 
those  minerals  which  contain  the  least  water,  hydrogen,  and  oxygen, 
will  leave  the  greatest  amount  of  carbon,  inasmuch  as  carbon  can- 
not be  evaporated,  without  access  of  another  element  with  which 
it  unites.  After  distillation,  a  certain  amount  of  carbon  is  left,  ac- 
cording to  the  preponderating  quantity  of  the  elements.  If  there 
should  be  a  great  deal  of  water,  hydrogen,  and  oxygen  in  the  raw 
material,  a  small  amount  of  carbon  will  be  left ;  should  there  be  a 
large  proportion  of  carbon  in  the  fuel,  a  large  amount  of  charcoal 
will  remain.  Wood,  turf,  and  brown  coal  generally  leave  a  char- 
coal in  precisely  the  form  in  which  the  pieces  were  put  into  the 
retort ;  their  porous  structure  permits  the  evolution  of  the  gases 


FUEL.  103 

without  disturbing  their  form.  Bituminous  coal  is  so  close,  and  its 
aggregates  so  compact,  that  the  escape  of  any  matter  from  the 
interior  is  impossible ;  its  bulk,  therefore,  is  increased  by  the  ap- 
plication of  heat ;  the  hydrogen  and  oxygen  which  escape  form 
small  cells,  and  the  remaining  carbon  is  spongy. 

The  presence  of  water  and  ashes,  as  well  as  of  hydrogen  and  oxygen 
to  a  large  amount,  in  fuel,  is  detrimental  to  iron,  even  in  the  pud- 
dling and  re-heating  furnaces;  and  still  more  injurious  in  the  blast 
furnace,  as  we  shall  hereafter  see.  To  avoid  these  influences,  at 
ledst  in  the  blast  furnace,  we  must  have  recourse  to  the  charring 
of  the  fuel ;  by  distilling  it,  we  get  rid  of  the  injurious  admixtures. 

V.   Charring  of  Wood. 

If  a  piece  of  wood  is  heated  until  it  kindles,  a  flame  issues,  which 
is  nourished  by  the  decomposition  of  the  wood ;  this  decomposition 
is  the  result  of  heat,  and  is  continued  by  the  heat  produced  by  the 
flame  itself.  Within  the  flame  is  a  dark  body,  carbon,  which  does 
not  burn  until  all  the  hydrogen  which  protects  it  is  consumed;  and 
only  after  this  protection  ceases,  and  after  the  oxygen  of  the  atmo- 
sphere finds  access  to  the  ignited  carbon,  is  the  carbon  consumed, 
when  it  disappears  gradually,  leaving  more  or  less  incombustible 
matter,  i.  e.  white  ashes.  If  the  access  of  atmospheric  air  is  pre- 
vented after  the  hydrogen  and  oxygen  are  expelled  or  consumed,  a 
black  coal,  charcoal,  will  remain.  This  experiment  can  be  made 
in  a  simple  way.  If  we  take  a  long  chip  of  wood,  and  hold  the 
flame  high  until  it  is  properly  kindled,  and  then  turn  the  flame  sud- 
denly downwards  into  a  narrow  tube  with  a  bottom,  the  wood  burns 
only  above  the  neck  of  the  tube,  and  the  part  which  is  in  the  tube 
is  extinguished,  leaving  a  black  charcoal.  This  is,  in  the  main,  the 
principle  of  charring :  the  gaseous  matter  of  the  wood  is  kindled  ; 
its  water  driven  off;  hydrogen,  oxygen,  and  a  little  carbon  yield 
the  heat  by  which  they  are  expelled ;  the  access  of  atmospheric 
air  is  then  excluded,  and  charcoal  remains. 

There  are  various  modes  of  charring  wood,  differing  principally 
in  arrangement  and  manipulation.  Scientifically,  there  are  but 
two  methods  :  that  is,  producing  the  heat  for  charring  from  the 
material  to  be  charred ;  and  applying  exterior  heat,  by  means  of 
extra  fuel,  in  the  manner  we  employ  it  in  distillation.  We  shall 
describe  the  different  modes  in  historical  order,  and  shall  dwell 
mainly  upon  the  most  practical. 

a.   The  most  ancient  way  of  making  charcoal  is,  simply,  to  dig  a 


104  MANUFACTURE   OF   IRON. 

hole  in  some  dry  place ;  to  fill  it  with  wood,  and  to  burn  a  part  of 
the  wood  until  sufficient  heat  is  produced  to  char  it  thoroughly ; 
the  wood  is  then  covered  with  sod,  or  sand,  or  coal  dust,  to  keep 
the  air  out ;  and  charcoal  will  remain  in  the  pit.  The  proper  time 
of  throwing  on  the  covering  is  a  matter  of  practical  importance. 
This  mode  of  charring  is  very  imperfect,  and,  at  present,  is  prac- 
ticed only  among  uncultivated  nations ;  it  makes  bad,  light  fuel, 
and  furnishes  it  only  in  small  quantity. 

b.  Charring  in  Heaps,  Kilns. — To  build  a  kiln  or  heap,  a  dry, 
sandy,  and,  when  possible,  level  spot,  in  the  woods,  is  selected, 
protected  from  wind  and  gales,  and  as  close  to  the  cord  wood  as 
possible ;  the  earth  is  to  be  leveled,  dug,  and  tilled,  to  remove  stones 
and  stumps,  and  sufficiently  large  to  permit  the  building  of  a  heap 
of  thirty  feet  in  diameter.  A  circular  space  of  from  forty  to  fifty 
feet  diameter  will  thus  be  required.  Great  care  should  be  taken 
that  no  spring,  or  water  of  any  kind,  is  in  the  neighborhood  of  the 
level,  and  that  sudden  gusts  of  rain  shall  not  overflow  it.  When 
the  ground  is  leveled,  and  pounded  as  solidly  as  possible,  the  haul- 
ing of  cord  wood  should  be  commenced ;  this  wood  must  be  piled 
vertically  around  the  circumference  of  the  hearth  or  level,  as  re- 
presented in  Fig.  24.  The  opening  «,  sufficiently  large  for  a  sled 
to  enter,  is  left  on  the  most  convenient  part  of  the  ground,  ac- 
cessible by  horses  or  oxen. 

Fig.  24. 


Hauling  the  wood  to  the  hearth. 

After  all  the  wood  is  put  around  the  hearth,  the  heaviest  billets 
always  to  be  placed  inside,  the  collier  puts  either  one  stick,  or,  what 
is  better,  three  stout  sticks  of  about  ten  feet  in  length,  right  in  the 
centre  of  the  hearth,  fixes  them  firmly  in  the  ground,  and  then 
fastens  or  binds  them  with  withes,  so  as  to  form  a  chimney  or 
draft-hole  in  the  centre  of  the  hearth,  as  seen  in  Fig.  25. 

The  collier  then  commences  to  set  his  kiln,  or  pit,  as  it  is  some- 
times called,  by  ranging  the  heaviest  billets  around  the  centre,  at 
first  vertically,  and  then  gradually  in  a  slanting  position  by  turning 
the  butt,  or  thickest  end  of  the  wood,  downwards.  The  wood  should 


FUEL.  105 


be  put  as  closely  together  as  possible,  that  it  may  be  brought  into 
the  narrowest  space.   After  it  is  all  set,  the  pile  (which  may  amount 


Setting  the  wood  for  charring. 

at  the  first  burning  to  twenty  or  twenty-two  cords,  and  may  be 
afterwards  increased  to  forty,  even  fifty  cords,  according  to  the  skill 
of  the  collier  and  quality  of  the  dust)  is  covered  with  small  limbs, 
cut  short,  and  with  chips,  &c.,  to  fill  the  crevices ;  in  fact,  the  pile 
must  be  made  as  smooth  and  tight  as  possible.  The  whole  kiln 
must  then  be  covered  with  leaves,  about  two  inches  thick.  Some 
colliers  are  in  the  habit  of  firing  the  kiln  as  soon  as  the  leaves  are 
thrown  on ;  but  this  practice  is  a  dangerous  one,  for,  should  a  gale  hap- 
pen to  blow,  or  should  it  become  windy  before  the  workmen  are  able 
to  cover  the  leaves  with  dust,  a  quantity  of  wood  and  coal  is  lost.  In 
addition  to  this,  very  dexterous  workmen  are  required  to  manage 
such  a  proceeding  advantageously.  The  best  way  to  proceed  is,  to 
cover  the  leaves  with  a  thin  layer  of  dust  before  fire  is  put  to  the 
kiln.  The  first  layer  of  dust  should  be  pure  earth,  and  somewhat 
short,  sandy,  and  by  no  means  tough  or  clayish,  for  in  the  latter 
case  it  will  shrink,  bake,  and  crack.  Besides,  it  is  almost  impossible 
to  keep  it  tight.  Where  no  other  dust  than  this  can  be  found,  it  is 
necessary  to  take  sod,  which,  of  course,  is  somewhat  expensive. 
The  first  dust  is  always  imperfect,  but  gets  better  with  the  progress 
of  the  work ;  for,  after  the  first  burning  and  drawing  of  coal,  it  is 
properly  made  by  mixing  the  green  dust  with  charcoal  dust.  This 
mixture  forms  a  light  open  cover,  admitting  frequently  a  thickness  of 
eight  inches,  and  is  of  course  the  most  secure  and  profitable.  Where 
coke  dust  can  be  had  at  a  reasonable  price,  it  is  the  most  available 
of  all  dusts.  After  the  whole  kiln,  with  the  exception  of  a  few  feet 
on  the  top,  is  covered  by  a  slight  coating,  the  fire  may  be  put  in 


106 


MANUFACTURE   OF   IRON. 


either  by  means  of  chips,  brands,  or  good  charcoal.  It  should  be 
kindled  at  the  bottom  of  the  centre,  at  a,  Fig.  25,  and  must  be 
watched  until  it  has  fairly  started;  the  kiln  may  then  be  left 
alone  for  at  least  twelve  hours,  provided  the  weather  is  not  so  stormy 
as  to  blow  the  cover  off.  Within  twelve  or  eighteen  hours,  the  kiln 
will  be  sufficiently  heated  to  permit  the  application  of  more  dust, 
and  the  closing  of  the  top ;  but  this  depends  greatly  on  the  skill  of 
the  collier,  and  the  kind  of  wood  to  be  charred.  Pine  and  dry  wood 
will  permit  more  time;  but  young  wood,  saplings,  hickory,  and 
maple,  require  closing  very  soon,  or  the  kiln  will  get  too  hot,  and 
a  great  deal  of  coal  will  thus  be  wasted.  Three  days,  or,  still 
better,  four  days  after  the  fire  is  started,  the  cover  gradually  sinks, 
and  this  is  the  time  that  the  hands  should  watch  closely;  for,  should 
the  heat  not  have  been  regularly  distributed  inside  the  kiln,  the 
setting  or  sinking  will  be  irregular,  and  the  cover  be  very  apt  to 
leave  openings,  where  the  atmosphere,  penetrating,  would  do  great 
damage,  in  case  such  breaks  are  not  directly  closed.  If  the  work 
has  been  well  conducted,  the  cover  sinks  gradually  and  regularly, 
and  the  dust  can  be  gradually  increased,  as  the  smoke  ceases. 
After  the  smoke  altogether  ceases,  the  whole  kiln  may  be  closely 
covered,  and  left  for  cooling.  Four  or  five  days  are  sufficient  to 
cool  the  kiln.  As  it  is  cooling,  the  drawing  of  coal  commences. 
This  is  performed  by  raking  the  dust  off  from  the  coal  at  the  foot 
of  the  kiln.  We  should  be  cautious  not  to  open  too  much  at  once, 
for  fresh  coal,  even  when  black  and  cold,  is  very  apt  to  rekindle,  and 

Fig.  26. 


Making  charcoal  in  heaps. 


FUEL.  107 

thus  occasion  a  loss  of  coal  and  time.  If  the  charcoal  is  sufficiently 
cold,  and  does  not  kindle,  the  drawing  may  be  continued  all  around 
the  kiln,  but  not  to  a  greater  extent  than  is  needed  to  fill  a  wagon 
load ;  the  kiln  is  then  to  be  carefully  covered,  and  left  until  the  next 
wagon  is  ready  to  take  a  load.  Sometimes  it  will  happen  that  the 
top  sinks,  or  that  the  fire  is  not  properly  kindled.  In  this  case,  the 
workmen  must  get  on  the  very  top  of  the  kiln.  That  this  may  be 
done  conveniently,  a  rough  stairs  or  ladder  is  made  of  a  round  stick 
six  or  eight  inches  thick,  as  shown  in  Fig.  26.  In  case  the  cover 
is  too  heavy,  or  in  case  the  fire  draws  to  one  side — a  circumstance 
which,  in  stormy  weather,  frequently  happens — the  hot  places 
should  receive  more  covering ;  and  in  the  cold  parts,  holes  should 
be  opened  by  removing  the  dust.  If  the  kiln  is  too  cold  at  the 
base,  holes  should  be  made  all  around,  that  the  fire  may  be  drawn 
towards  the  bottom. 

The  foregoing  description  of  charring  applies  to  the  standing 
kiln.  It  is  a  mode  of  working  very  much  in  use,  and,  by  care  and 
attention,  furnishes  good  results.  There  is,  however,  one  objection 
to  it ;  that  is,  if  the  wood  is  very  cylindrical,  or  if  one  end  is  as 
thick  as  the  other,  many  spaces  will  be  left  which  cannot  be  filled. 
These  are  injurious  to  the  final  result ;  for  the  circumference  of  the 
kiln  will  require  to  be  sloped  to  make  the  dust  stick;  and  to  "make 
that  slope  the  wood  must  be  drawn  outward  at  the  base.  To  avoid 
such  spaces  between  the  billets,  another  method  is  frequently 
adopted :  that  is,  setting  the  wood  around  the  centre  post  verti- 
cally, and  the  last  four  feet  at  the  circumference  horizontally,  as 
represented  in  Fig.  27 ;  but  the  advantages  afforded  by  this  method 

Fig.  27. 


Section  of  a  charcoal  work — piling  the  wood. 


108  MANUFACTURE   OF   IRON. 

are  not  great ;  and  it  is  of  but  little  consequence  which  method  is 
pursued.  Care  and  attention  on  the  part  of  the  workmen  are  the 
guarantee  of  success.  The  time  required  to  finish  a  burning  dif- 
fers, and  depends  on  the  season,  weather,  wood,  dust,  capacity  of 
the  workmen,  and  other  circumstances.  Winter  is  always  a  bad 
season  for  charring. 

Stormy,  rough  winds  are  equally  unfavorable ;  green  wood  fur- 
nishes a  poor  yield,  and  bad  coal;  green  or  heavy  dust  is  disad- 
vantageous ;  light  dust  is  equally  so.  Colliers  who  do  not  under- 
stand their  business,  or  who  are  not  industrious  and  attentive, 
never  make  good  coal,  nor  produce  a  good  yield.  If  the  work  is 
unreasonably  hurried,  or  if  the  teams  are  not  always  ready  at  the 
proper  time,  unavoidable  losses  are  the  consequence. 

c.  Charring  in  Mounds. — One  of  the  most  ancient  modes  of  char- 
ring wood  is  by  mounds.  This  method  is  practiced  to  a  great  ex-^ 
tent  in  the  pine  forests  of  Austria ;  and  for  pine,  or  well-seasoned 
hard  wood,  deserves  our  notice.  A  mound  is  built  in  the  following 
manner  :  Fig.  28.  A  row  of  posts,  a,  is  firmly  fastened  into  the 

Fig.  28. 


Wood-charring  mound. 

ground.  The  ground  should  be  previously  leveled  or  sloped.  A 
second  row  5,  parallel  with  the  first,  and  well  secured,  must  then  be 
similarly  placed ;  the  distance  between  the  two  rows  is,  by  four  feet 
long  cord  wood,  eight  feet  eight  inches.  The  length  of  such  a  row 
will  depend  upon  the  dimensions  of  the  mound,  say  from  forty  to 
fifty  feet,  and  the  posts  ought  to  be  no  more  than  four  feet  distant 
from  each  other ;  the  post  c  will  be  six  feet,  and  d  only  three  feet 
above  ground.  Three  head  posts,  0,  are  then  put  in,  and  the  whole 
inside  of  the  frame  is  lined  with  boards,  lath,  slabs,  or  even  with 
split  cord  wood.  This  lining  is  to  be  fastened  to  the  posts  by  wooden 
pins.  After  the  frame  is  finished,  the  lining  fastened,  and  the  floor 


FUEL.  109 

pounded  solidly  down,  the  setting  is  commenced,  by  throwing  the 
wood  crosswise  on  the  floor;  and,  beginning  at  e,  the  woo$  is 
gradually  piled  to  within  three  inches  of  the  top  of  the  lining. 
By  packing  the  wood  closely,  a  mound  fifty  feet  in  length,  six 
feet  in  height  at  the  head,  and  three  at  the  foot,  and  eight  feet 
eight  inches  wide,  ought  to  take  from  twelve  to  fourteen  cords  of 
wood.  The  wood,  if  not  too  heavy,  that  is,  if  not  more  than  twelve 
or  fifteen  inches  in  diameter,  may  be  round ;  and  if  straight,  eight 
feet  in  length.  In  that  case,  it  packs  more  closely  than  split  wood. 
By  laying  the  wood  crosswise  throughout  the  length  of  the  mound, 
the  advantage  of  fast  work  is  secured,  for  the  coal  can  then  be 
drawn  gradually  as  the  fire  retires.  After  the  wood  is  all  in,  and 
the  top  leveled  with  limbs  or  chips,  a  dust,  sod,  or  sand  cover  is 
thrown  over  the  whole  ;  the  sides,  where  a  space  all  around  is  to  be 
left,  are  equally  filled  between  the  lining  and  the  wood  with  dust, 
which  must  be  firmly  pounded  in,  to  prevent  the  lining  from  catch- 
ing fire.  When  the  whole  mound  is  covered,  fire  is  kindled  at  the 
lower  end/.  In  the  mean  time,  some  dust  is  removed  at  the  top, 
near  c.  After  the  lapse  of  a  few  hours,  the  fire  will  be  sufficiently 
advanced  to  permit  the  egress  of  smoke  at  e\  and  the  dust  at/  may 
be  thrown  on  again.  To  secure  a  supply  of  fresh  air,  one  of  the 
draft-holes  g,  g,  on  each  side,  may  be  opened.  By  this  method,  the 
charring  proceeds  rapidly,  and  requires  watching.  When  the  fire 
has  advanced  about  ten  feet,  which  will  require  a  period  of  twenty- 
four  hours,  coal  may  be  drawn  at  /,  and  continually  drawn  until 
close  to  the  fire.  This  latter  advantage  is  mainly  due  to  the 
sloping  of  the  wood  pile ;  and  it  is  still  greater  if  the  pile  is  put  on 
a  gently  sloping  hillside. 

This  process  of  making  charcoal  is  a  very  ancient  one.  It 
was  employed  by  the  Romans  to  manufacture  charcoal  for  their 
forges  ;  and  at  the  present  day,  in  the  very  country  where  the 
ancient  Romans  carried  on  their  iron  establishments,  this  mode 
of  charring  is  preferred  to  all  others.  The  process  now  carried 
on  in  southern  Austria  differs  not  in  the  least  from  that  in  use 
at  the  time  of  Pliny.  It  is  one  of  those  inventions  which  a  com- 
prehensive genius  finished,  and  left  to  posterity  nothing  but  the  task 
of  explaining ;  it  is  so  simple,  practical,  and  complete,  that  no  im- 
provement is  possible.  How  it  happens  that  we,  at  the  present 
day,  in  more  cultivated  countries,  reflect  so  little  upon  this  most 
simple  and  perfect  mode  of  charring  wood,  is  more  than  we  are 


110 


MANUFACTURE    OF  IRON. 


able  to  explain.  We  have  both  observed  and  practiced  it,  and  have 
found  it  to  answer  all  the  claims  of  the  iron  master.  It  delivers  a 
strong  coal,  and  yields  well.  It  combines  the  advantages  of  the  pit, 
the  kiln,  and  the  char-oven.  At  the  close  of  this  chapter,  we  shall 
elucidate  this  subject  more  fully. 

d.  Charring  in  Ovens. — The  inducements  to  invent  ovens  for 
charring  wood,  coal,  lignite,  and  turf,  were,  partly  a  desire  of  gaining 
the  gaseous  educts  of  the  charring  process,  and  partly  a  desire  of 
security  against  wind  and  storms.  The  first  object  is  only  imper- 
fectly realized ;  because,  if  the  fuel  for  distillation  is  derived  from  the 
material  to  be  charred,  the  combinations  of  hydrogen  and  carbon  are 
mostly  destroyed,  while  nothing  but  tar  and  heavy  carbonized  com- 
pounds are  the  result  of  the  distillation.  Even  this  is  to  be  gained 
only  by  impairing  the  quality  of  the  charcoal.  The  latter  object  is 
available ;  a  well-built  oven  affords  perfect  security  against  wind  and 
storm ;  and  where  the  transport  of  wood  to  a  general  charring  place 
is  not  too  high,  great  advantages  may  be  derived  from  it.  Of  the 
various  improvements  adapted  to  the  principle  of  charring  in  ovens, 
the  French  have  furnished  the  largest  proportion.  They  have  been 
compelled,  by  the  scarcity  of  fuel  in  France,  to  direct  their  experi- 
ments with  the  especial  object  of  economizing  it.  The  building  of 
stationary  char-ovens  has  been  brought  to  a  state  of  perfection.  With 
good  bricklayers,  all  that  is  required  to  build  a  good  oven  is  close 
joints  and  good  sound  brick.  The  form  of  these  ovens  has  been 
varied  to  suit  almost  every  notion  ;  still  it  is  generally  agreed  that 
ovens  of  less  capacity  than  fifty,  and  of  greater  capacity  than  sixty 
cords,  are  less  advantageous  than  those  constructed  within  these 
limits.  A  further  distinction  is  made  between  ovens  for  making 
black,  and  those  for  making  brown,  charcoal.  The  first  are  heated 
with  their  own,  the  latter  by  additional,  fuel.  A  description  of  the 


Wood-charring  oven. 


FUEL. 


Ill 


Section  of  wood  charring  oven. 


various  forms  of  these  ovens  would  occupy  too  much  space ;  there- 
fore, we  shall  notice  simply  the  latest  improved  oven  of  each 
kind.  Fig.  29  represents  a  char-oven  for  wood,  now  in  use  near 
Baltimore.  A  is  a  side  elevation, 
showing  the  binders  a,  a,  a,  made 
of  cast  iron;  these  stays  or  binders 
may  be  made  of  eight  inch  timber, 
hewn  on  two  sides ;  but  iron  has 
a  much  better  appearance.  The 
cross  binders  5,  5,  5,  b  are  made 
of  one  inch  square  wrought  iron 
bar,  either  with  head  and  screw, 
or  with  head  and  key ;  either  will 
answer  the  purpose.  The  distance  between  two  binders  should 
not  be  more  than  four  feet,  and  if  possible  less  than  that ;  <?,<?,<? 
are  draft-holes,  just  the  size  of  a  common  brick  cross  section,  for 
the  regulation  of  the  fire ;  these  must  be  closed,  or  opened,  as  the 
charring  of  the  wood  progresses.  j£,  Fig.  30,  is  a  cross  section  of 
the  oven ;  in  the  brick  arch  c?,  a  square  opening  e,  eighteen  inches 
wide,  is  left ;  this  opening  may  be  shut,  when  necessary,  with  an 
iron  plate.  At  each  end  of  the  oven  there  is  a  door  /,  large  enough 
to  admit  a  man  with  a  wheelbarrow.  These  openings  serve  the 
purpose  of  charging  the  oven,  and  drawing  the  coal.  A  far  better 
arrangement  than  these  small  doors  at  each  end  of  the  oven  is 
to  shut  one  end  entirely  with  brick,  and  leave  the  other  entirely 
open ;  or  at  least  to  leave  an  opening  sufficiently  large  to  permit 
the  entrance  of  a  horse  and  cart,  and  then  to  shut  this  opening 
with  large  double  doors,  secured  inside  by  a  heavy  coating  of  loam. 
The  bottom  of  the  oven  is  covered  with  sand,  or,  what  is  still  better, 
coal  dust  well  pounded  down.  The  perfect  air-tightness  of  the 
brickwork  is  of  the  highest  importance ;  the  bricklayers  require  to 
be  watched,  as  well  as  instructed.  Common  brickwork  will  not 
do.  All  the  joints,  in  addition  to  being  completely  filled  with 
mortar,  should  be  regularly  broken.  The  wall  should  be  one  brick 
and  a  half  thick.  Common  mortar  of  lime  and  sand  should  not 
be  used,  for  the  acetic  acid  of  the  wood  dissolves  the  lime,  and 
leaves  the  sand  alone  in  the  joints.  Common  loam,  mixed  with 
coal  tar  or  sea  salt,  makes  an  excellent  mortar. 

The  inside  of  the  oven  should  be  well  smoothed,  and  all  the 
joints  filled.  Coatings  of  coal  tar  are  the  best  covering  for  the 
outside  ;  these,  besides  securing  the  durability  of  bricks  and  mor- 


112  MANUFACTURE  OF   IRON. 

tar,  close  small  crevices,  and  strengthen  the  walls.  Such  ovens 
are  usually  built  twelve  feet  in  width,  twelve  feet  in  height,  and 
fifty  feet  in  length ;  seldom  larger.  An  oven  of  this  size  ought 
to  contain  fifty-five  cords  of  wood. 

The  wood  is  laid  flat,  and  piled  row  by  row  until  the  oven  is 
filled.  In  the  centre,  from  the  hole  e,  a  channel  or  chimney  is  left, 
about  twelve  or  fifteen  inches  in  diameter,  for  the  purpose  of  en- 
abling us  to  kindle  the  wood  right  at  the  bottom.  Some  kindle  at 
the  draft-holes  c,  <?,  or  at  the  doors  at  both  ends;  but  the  former  is 
the  preferable  plan.  After  the  oven  is  filled,  the  doors  closed  and 
well  secured,  the  air-holes  shut  with  a  brickbat,  and  every  access  of 
air  into  the  oven  prevented,  a  fire  of  charcoal  brands  or  of  dry  wood 
may  be  thrown  down  through  e  ;  this  will  kindle  the  wood  at  the 
bottom  of  the  pile.  After  the  fire  is  fairly  started,  the  chimney  may 
be  filled  with  dry  cord  wood;  and  in  the  mean  time,  on  each  of  the 
four  corners  an  air-hole  is  opened.  Within  six  or  eight  hours  the 
fire  in  the  interior  will  be  sufficiently  spread  to  permit  the  opening 
of  a  few  more  air-holes  at  both  ends  of  the  kiln.  When  the  heat 
draws  near,  these  ends  may  be  shut,  and  some  air-holes  opened 
along  the  sides.  By  alternately  shutting  and  opening  air-holes, 
according  to  necessity,  the  oven  will  be  sufficiently  heated  within 
forty-eight  hours.  This  maybe  determined  by  the  escape  of  brown 
smoke  from  e.  After  the  steam  at  e  ceases,  and  a  dark  yellow  or 
brown  smoke  escapes,  the  heatin  the  interior  is  sufficiently  developed 
to  char  that  wood  which  is  not  touched  by  fire.  The  top  hole  e 
may  be  tightly  closed  either  with  an  iron  plate,  or  with  a  board, 
covered  with  moist  loam.  The  smoke  will  now  escape  from  the 
air-holes  around  the  oven ;  these  must  be  gradually  closed  one 
after  another,  and  then  secured  by  shutting  the  joints  with  mois' 
loam.  Three  days  must  elapse  before  the  charcoal  is  sufficiently 
cool  to  be  drawn ;  if  an  oven  does  not  cool  in  that  time,  either  air- 
holes must  be  open,  or  the  brickwork  cannot  be  tight.  To  remedy 
this  evil,  the  outside  of  the  oven  should  be  covered  with  a  thin  wash 
of  loam  water,  mixed  with  sea  salt,  that  all  invisible  cracks  and  joints 
may  be  closed.  After  this  wash  is  dry,  it  may  be  covered  with 
a  good  coating  of  coal  tar.  If  the  oven  is  in  proper  order,  the 
cover  on  e  may  be  taken  off,  and  a  few  air-holes  opened.  Should 
no  smoke  or  heat  escape,  within  two  hours,  from  e,  the  doors  may 
be  opened,  and  the  coal  drawn,  and  carried  off. 

Ovens  of  this  description  afford  great  advantages  where  a  good 
supply  of  wood  can  be  obtained.    They  furnish  a  strong  and  coarse 


FUEL.  113 

coal  for  the  blast  furnace,  but  do  not  answer  so  well  for  forge  coal. 
Forge  coal  is  best  made  in  pits  or  kilns. 

e.  Where  wood  is  scarce,  and  economy  of  fuel,  therefore,  an  ob- 
ject, brown  charcoal  or  brown  wood  is  frequently  used  in  the  blast 
furnace.  The  wood,  in  this  case,  is  only  strongly  dried  or  roasted. 
For  this  purpose,  an  oven  about  twenty-five  feet  long,  half  the  size 
of  the  first,  is  required.  Its  form  is  similar  to  that  of  Fig.  29, 
with  this  difference,  that  it  contains  no  air-holes ;  while  four  flues 
in  the  bottom,  made  of  brickwork,  run  its  whole  length.  These 
flues  are  eighteen  inches  wide,  arched  at  the  top.  In  the  top  of  the 
flues,  at  intervals  of  two  or  three  feet,  draft-holes  are  left,  through 
which  a  large  quantity  of  heated  air  can  pass. 

Fig.  31. 


Ground-plan  of  a  wood-drying  oven. 

Fig.  31  exhibits  a  ground-plan  of  the  flues ;  the  channels  a,  a 
project  about  a  foot  at  each  end,  to  permit  the  closing  of  the  doors 
with  safety.  The  oven  is  charged  with  wood,  as  in  Fig.  29 ;  but 
it  is  without  a  chimney  in  the  centre.  After  the  doors  are  closed, 
and  everything  else  well  secured,  fire  is  kindled  at  a,  a,  a,  a,  and 
kept  going  with  sawdust,  green  chips,  or  with  any  slow  burning 
fuel.  Turf  or  brown  coal  will  answer  quite  as  well  as  anything 
else.  The  fire  must  be  so  regulated  as  to  let  a  large  amount  of  air 
pass  over  it,  get  heated,  and  pass  through  the  wood.  By  this 
method,  wood  will  dry  very  fast :  in  thirty-six  hours,  twenty-five 
cords  will  be  in  a  condition  fit  to  be  drawn,  in  case  the  manipula- 
tions have  been  properly  conducted.  But  great  care  is  to  be  taken 
that  the  temperature  of  the  fire  is  kept  so  low  that  the  cord  wood 
cannot  catch.  Should  such  an  accident  happen,  the  top  is  to  be 
closed  directly,  and  the  fire-places  shut  up. 

How  far  the  wood  should  be  charred,  depends  on  circumstances. 
A  charring  sufficient  to  permit  the  breaking  of  the  billets  by  hand, 
will  be  indicated  by  a  dark  brown  color  of  the  wood  ;  such  wood 
works  well  when  mixed  with  charcoal  or  coke ;  it  keeps  the  blast 


114  MANUFACTURE   OF  IRON. 

furnace  open,  and  bears  a  stronger  blast  than  charcoal  alone.  In 
France,  Germany,  and  Russia,  brown  charcoal  is  frequently  used. 

/.  Another  method  by  which  charcoal  is  manufactured  from  wood, 
is  by  distillation  in  closed  vessels.  This  is  a  very  imperfect  method ; 
for  the  coal  derived  from  this  source  is  friable,  soft,  and  very  apt  to 
choke  a  furnace.  It  bears  but  little  blast,  and  is  only  adapted  to 
ores  easily  worked.  This  kind  of  work  belongs  to  chemical  facto- 
ries, where  the  charcoal  is  considered  of  secondary  importance.  The 
produce  of  distillation  is  chiefly  wood  vinegar,  or  acetic  acid,  called 
pyroligneous  acid,  besides  other  compounds.  Nevertheless,  an  ap- 
paratus for  the  distillation  of  the  products  of  wood,  invented  and 
constructed  by  the  celebrated  Mr.  Reichenbach,  deserves  our  atten- 
tion for  a  few  moments.  Reichenbach  was  the  discoverer  of  creasote 
and  of  other  celebrated  wood  products.  The  ovens  of  his  invention, 
erected  at  iron  works  in  Austria,  are  large,  tower-like  buildings. 
An  oven  of  this  kind,  about  twenty  feet  square,  and  from  twenty  to 
twenty-five  feet  high,  is  well  built  of  brick  work,  without  roof  or 
top  arch,  and  secured  with  wooden  or  iron  binders.  At  the  lower 
part,  a  few  feet  from  the  bottom,  is  a  series  of  cast  iron  pipes,  twelve 
inches  in  diameter,  which  serve  the  purpose  of  flues.  Such  an 
oven,  filled  with  cord  wood,  covered  on  the  top  with  sod,  slabs,  or 
coal  dust,  and  on  that  account  movable,  when  well  secured  against 
draft  of  air  into  its  interior,  is  kindled  from  a  furnace  which  com- 
municates with  the  iron  pipes,  and  kept  in  a  lively  blaze  ;  the 
iron  pipes  conduct  their  heat  to  the  wood,  which  gets  charred. 
The  main  purpose  of  this  oven  is  to  collect  the  products  of  the 
distillation.  For  this  purpose,  a  large  channel  behind  the  oven 
runs  below  ground,  which  is  kept  cool  by  a  constant  flow  of  water 
over  iron  plates  on  its  top;  into  this  channel,  or  condenser,  the  pro- 
ducts of  the  distillation  are  conducted  in  iron  pipes,  whence  they 
are  gathered.  A  chemical  factory  is  connected  with  this  charring 
apparatus.  Like  distillation  in  iron  retorts,  distillation  in  ovens 
is  of  no  use  for  making  charcoal  for  the  blast  furnace,  because 
the  coal  produced  is  very  soft  and  brittle,  and  does  not  bear  blast 
nor  burden. 

g.  G-eneral  Remarks. — The  charring  of  wood  is,  to  the  manufac- 
turer of  iron,  a  subject  of  the  greatest  importance.  His  business  re- 
quires a  strong,  compact,  heavy  charcoal.  We  will,  therefore,  de- 
lineate those  leading  principles  by  which  the  quality  and  quantity 
most  advantageous  to  him  may  be  obtained.  Charcoal  obtained  by 
the  action  of  a  rapid  fire  in  close  vessels,  or  in  the  open  air,  is  light, 


FUEL.  115 

spongy,  and  friable,  and  unfit  for  his  purpose.  Wood  charred  in 
an  iron  retort  furnished,  according  to  a  French  experimenter,  within 
three  hours,  eighty-eight  parts  of  charcoal ;  within  four  hours,  ninety 
parts;  and  within  five  hours  113  parts.  Beyond  this  time,  instead 
of  an  increase,  there  was  a  decrease  of  charcoal.  It  is  proper  to  re- 
mark, that  a  well-conducted  kiln  furnished,  on  the  same  principle, 
106  parts  of  charcoal ;  this  result  clearly  shows  the  utility  of  kiln 
charring.  But  there  is  a  limit  in  both  cases.  Too  quick  and  too 
slow  work  are  equally  injurious.  We  should  always  be  governed 
by  the  following  facts  in  our  operations :  If  the  charring  is  pushed 
too  fast,  or  if,  from  the  kindling  of  the  wood,  it  is  too  lively,  the  coal 
will  be  small,  light,  and  the  yield  will  be  meagre.  If,  on  the  con- 
trary, charring  proceeds  slowly,  the  coal  will  be  light  and  friable; 
though  the  yield,  if  the  cover  has  been  kept  tight,  will  be  good. 

h.  The  yield  varies  considerably,  according  to  the  quality  of  wood, 
and  the  kind  of  timber.  Mr.  Mushet  gives,  as  the  result  of  char- 
ring on  the  small  scale,  with  due  consideration  of  the  form  of  the 
pieces  of  wood,  the  following  comparison,  in  which  one  hundred 
parts  in  weight  of  dry  wood  were  taken  for  each  trial  :— 

Mahogany  -  25.4 

Chestnut  -  23.2 

Oak  -  22.6 

Walnut     -  20.6 

Beech  -  19.9 

Sycamore  -  19.7 

Pine  -  19.2 

Ash  -  17.9 

Birch  -  17.4 

So  uniform  a  result  depends,  however,  very  much  on  the  uniform 
structure  and  dryness  of  the  wood ;  conditions  not  always  at  our 
command  either  in  the  woods  or  in  the  yard.  Season,  and  the  age, 
as  well  as  the  dryness,  of  the  wood,  influence  greatly  both  the  yield 
and  quality  of  coal.  Experience  has  taught  us  this  fact ;  and  it 
is  beautifully  illustrated  in  the  following  table  by  M.  Berthier,  a 
French  chemist.  The  wood  used  in  his  experiments,  where  not 
otherwise  mentioned,  was  thirty-two  years  old,  and  was  charred 
in  common  kilns,  under  the  same  conditions.  The  table  shows  the 
per  centage  of  coal  yielded  in  one  hundred  parts : — 


116  MANUFACTURE   OF  IRON. 

Coal.  Brands 

Green  red  beech,  charred  shortly  after  being  cut,  19.7  0.6 

"  "  "         "  "       peeled,  23.0  0.3 

Dry  red  beech  and  oak,  of  two  years'  standing,  24.0  0.3 

"  oak,  "  "  *  "  peeled,  25.7  0.3 

Green  white  oak,  charred  three  months  after  being  cut,  22.4  0.3 

"  "  "  "  "  peeled,  21.2  0.3 

Red  beech  and  oak,  cut  in  January,  and  charred  in 

August,  23.4  0.5 

Green  red  beech,  charred  immediately  after  being  cut,  12.9  0.3 

"        oak,          "  "  "  "          13.5  0.4 

We  thus  see  that  one  hundred  pounds  of  wood  in  kilns  produce, 
on  an  average,  twenty  pounds  of  charcoal.  In  retorts  and  ovens, 
the  amount  seldom  exceeds  twenty-two  pounds.  The  advantage, 
therefore,  of  employing  ovens,  apart  from  other  considerations, 
is  not  great ;  but  this  is  the  ground  of  preference.  Ovens  are 
advantageous  where  wood  can  be  transported  on  water;  this  trans- 
portation charcoal  cannot  bear  without  injury.  Charcoal  absorbs 
water  and  gases  in  large  quantities ;  and  what  it  gains  in  specific 
gravity  it  loses  in  combustibility;  still,  it  is  generally  preferable  for 
making  iron.  On  what  hypothesis  this  anomaly  is  to  be  explained, 
we  are  unable  to  say.  We  simply  mention  it  as  an  established  fact. 
Charcoal  will  absorb  a  large  amount  of  water  within  the  first  twenty- 
four  tours ;  but,  after  that  time,  very  little.  Different  kinds  of 
charcoal  absorb  water  in  different  quantities,  to  wit : — 
Charcoal  from  lignum  vitse  gained  9.6  per  cent. 
"  fir  "  13.0  " 

"  box  "     14.0        « 

"  beech  "     16.3         " 

"  oak  «     16.5        " 

"  mahogany          "     18.0         " 

That  water  cannot  be  the  cause  of  improvement,  is  evident.  To 
assist  those  who  desire  to  investigate  this  subject,  we  subjoin  a 
table  on  the  absorption  of  gases  by  charcoal  within  the  first  twenty- 
four  hours  after  charring.  One  hundred  parts  of  charcoal  absorbed 

Ammoniacal  gas      -  90  per  cent. 

Muriatic  gas  85       " 

Sulphurous  acid       -  55       " 

Sulphuretted  hydrogen  -  55       " 

Nitrous  oxide  40       " 


FUEL.  117 

Carbonic  acid  gas     -  35      per  cent. 

Bicarburetted  hydrogen  -                           35  " 

Carbonic  oxide  9.42  " 

Oxygen  9.25  " 

Nitrogen  7.50  " 

Carburetted  hydrogen  -                             5.00  " 

Hydrogen  ¥.75  " 

i.  Many  iron  manufacturers  desire  to  realize  the  products  of 
distillation;  but  the  deficiency  in  the  quality  of  the  charcoal  more 
than  counterbalances  the  whole  gain  of  the  distillation.  The  iron 
master  will  employ  his  time  far  more  profitably  by  cultivating  the 
charring  for  the  production  of  charcoal  alone. 

Jc.  The  time  best  adapted  for  charring,  in  the  woods,  is  from  May 
till  October  inclusive.  During  the  summer,  the  air  is  bland,  the 
roads  good,  and  the  furnace  yard  dry;  considerations  of  great 
importance.  The  price  of  charcoal  varies,  in  Pennsylvania  and 
the  neighboring  States,  from  four  to  six  cents  per  bushel  of  five 
pecks,  if  bought  in  the  yard.  Managers  ought  to  examine  closely 
the  specific  gravity  of  the  coal  before  buying,  for  slowly  charred 
coal  is  generally  twenty  per  cent,  lighter  than  properly  charred 
hard  coal,  made  from  the  same  wood.  A  bushel  of  five  pecks,  or  2675 
cubic  inches,  of  fresh  charcoal,  made  of  beech,  oak,  maple,  and 
hickory,  ought  to  weigh  from  fifteen  to  sixteen  pounds  ;  a  bushel  of 
pine  coal,  from  ten  to  eleven  pounds;  and  the  prices  paid  for  char- 
coal should  vary  accordingly.  The  wages  of  colliers  for  charring 
vary  from  one  dollar  twelve  and  a  half  to  one  dollar  and  twenty- 
five  cents  per  one  hundred  bushels ;  colliers  to  pay  their  hands,  to 
have  the  loan  of  tools,  to  have  the  wood  delivered  at  the  level,  and 
leaves.  From  seasoned  wood  the  yield  ought  to  be  forty  bushels 
per  cord  ;  the  loss  charged  to  the  collier.  At  this  rate,  the  collier 
should  be  permitted  to  form  his  own  judgment  whether  the  wood 
is  correctly  ranked.  If  found  deficient,  a  liberal  deduction  should 
be  granted.  If  the  collier  is  expected  to  furnish  a  given  yield,  a 
prompt  attendance  of  the  teams  is  required,  that  he  may  not  sus- 
tain loss  through  delay  in  hauling.  All  necessary  roads  must  be 
made  by  the  employer.  From  ten  to  twenty  cents,  according  to 
locality,  is  paid  for  the  hauling  of  wood  to  the  levels. 

VI.   Charring  of  Turf. 

The  charring  of  turf  is  far  more  easily  effected  than  the  charring 
of  wood,  partly  on  account  of  its  square  form,  partly  on  account  of 


118 


MANUFACTURE   OF   IRON. 


its  chemical  composition.  In  pits,  the  charring  of  turf  is  not  dif- 
ficult, if  we  pursue  the  same  method  as  that  pursued  in  the  charring 
of  wood;  but  we  are  forced  to  leave  channels,  or  draft-holes,  in  the 
kiln,  because  the  square  pieces  pack  so  closely,  that,  without  this 
precaution,  sufficient  draft  would  not  be  left  to  conduct  the  fire. 
Turf  is  generally  found  in  considerable  masses  in  one  spot ;  there- 
fore the  erection*6f  char-ovens  is  no  object  of  mere  speculation,  but 
affords  all  the  advantages  of  a  permanent  establishment.  Char-ovens 
for  turf  are  comparatively  small,  and  of  course  not  expensive.  We 
therefore  shall  omit  a  description  of  charring  in  pits,  and  shall  pro- 
ceed to  describe  a  char-oven,  which  has  been  in  use  for  more  than 
ten  years,  and  consequently  sufficiently  tested.  Fig.  32  represents  a 


Char-oven  for  turf. 

vertical  cylinder,  built  of  bricks,  with  a  round  cupola  on  the  top  ; 
it  is  nine  feet  high,  and  five  feet  and  a  half  in  diameter,  which  gives 
250  cubic  feet  capacity.  The  inner  cylinder  6,  built  of  fire  brick, 
is  surrounded  by  a  mantel  a  of  common  brick,  and  the  space  left  be- 
tween both  is  filled  with  sand.  Sometimes  a  brick  d  runs  all  the 
way  through,  to  bind  both  walls  ;  on  the  top  is  a  round  opening  c  ; 


FUEL.  119 

e  is  an  iron  plate  to  close  the  draft-hole  c ;  /  is  a  board,  or  a  piece  of 
sheet  iron,  to  hold  the  sand,  which  is  used  to  shut  the  air  out,  by 
filling  the  space  g.  The  turf  is  filled  in  at  c,  and  packed  closely, 
with  the  exception  of  a  few  channels  at  the  bottom,  which  corre- 
spond with  the  little  draft-holes  A,  A,  h.  A  vertical  chimney  is  left 
in  the  centre,  at  which  gases  may  escape.  The  fire  is  put  in 
through  e,  down  to  the  bottom ;  and  when  it  has  spread  so  far  as  to 
show  itself  at  the  holes  A,  A,  A,  these  holes  are  shut  by  a  stopper 
of  clay.  When  the  smoking  at  the  top  ceases,  all  the  openings, 
as  well  as  the  top,  are  to  be  shut ;  and  the  oven  left  for  cooling. 
Four  or  five  days  will,  in  most  cases,  be  sufficient  to  burn  an  oven 
of  turf  charcoal.  The  holes  7i,  A,  h  can  be  formed  of  old  gun  barrels 
or  iron  pipes;  bricks  or  earthenware  pipes  are  very  apt  to  break. 
Turf  charcoal  is  an  excellent  fuel,  but  expensive ;  it  burns  freely, 
and  produces  a  fine  heat.  In  Styria,  sheet  iron  and  re-heating  fur- 
naces are  heated  by  it :  and  in  Bohemia,  Bavaria,  France,  and  Rus- 
sia, it  is  extensively  used  in  the  blast  furnaces,  and  produces,  in 
most  cases,  very  liquid,  lively  iron.  Good  turf  coal  is  superior  to 
charcoal  in  the  blacksmith's  fire. 

VII.   Charring  of  Brown  Coal. 

Brown  coal  is  so  imperfect  a  fuel  in  most  cases,  that  it  scarcely 
ever  admits  of  being  charred ;  but  the  best  lignite  of  Europe  is 
charred,  though  only  with  limited  success.  The  subject  is  not  suf- 
ficiently important  to  occupy  our  attention. 

VIII.  Charring  of  Bituminous  Coal,  Coke. 

The  manufacture  of  coke  for  blast  furnace  purposes  is  generally 
carried  on  in  the  open  air,  either  in  round  heaps  or  rows ;  the  latter 
mode  is  generally  preferred.  Coke  burned  in  ovens  will  answer  for 
that  which  is  used  in  the  furnace  of  locomotives,  or  for  the  purpose 
of  generating  steam ;  it  is  even  useful  in  a  foundry  cupola  oven ; 
but  in  the  blast  furnace,  or  even  in  the  refining  fire,  it  ought  not  to 
be  applied,  for  reasons  we  shall  presently  explain. 

a.  Coking  in  heaps  is  almost  the  same  as  charring  wood  in  heaps; 
the  main  difference  is  that  the  heaps  are  smaller.  For  the  pur- 
pose of  coking  in  heaps,  a  level  spot  in  the  yard  is  selected,  or  a 
level  staked  out  and  prepared ;  a  temporary  chimney  of  common,  or 
even  of  fire  brick  is  erected,  with  alternate  holes,  some  of  which  are 
especially  necessary  at  the  base.  Around  this  chimney  coarse  coal 
is  piled ;  the  bottom,  or  level,  is  covered  with  coarse  coal,  in  which 


120  MANUFACTURE    OF   IRON. 

draft-channels  must  be  left ;  coal  may  then  be  thrown  on  as  it  comes; 
but  the  coarse  coal  must  be  put  in  the  centre  of  the  heap.  The 
height  is  of  but  little  consequence,  and  may  vary  from  three  to  six 
feet,  according  to  convenience.  But  the  chimney  is  to  be  built 
sufficiently  high  to  reach  over  the  top  of  the  coal  pile.  Fig.  83  re- 
Fig.  33. 


Coking  in  heaps. 

presents  such  a  kiln  or  heap ;  a  is  the  brick  chimney.  After  the 
heap  is  ready,  fire  may  be  kindled  around  the  base  at  different  places, 
particularly  near  the  horizontal  channels  ;  and  the  whole  pile  may 
then  be  slightly  covered  with  coke  dust.  The  fire  will  spread 
rapidly,  and,  in  a  few  hours,  will  reach  almost  to  the  centre.  A 
few  air-holes  may  now  be  made  in  the  cover  with  an  iron  bar, 
through  which  the  heat  and  smoke  may  have  vent.  These  air- 
holes should  be  frequently  renewed,  because  very  bituminous  coal  is 
apt,  by  swelling,  to  close  them.  If  the  fire  has  been  kindled  in 
the  morning,  the  heap  will  be  in  a  good  heat  towards  evening. 
It  may  then  be  covered  heavily  with  dust,  and  the  fire  all  around 
the  heap  choked.  But  the  chimney  is  to  be  left  open.  The  next 
day,  or,  at  farthest,  after  the  third  day,  the  coke  is  ready  for  use. 
The  object  of  leaving  the  chimney  open  is  to  retain  a  slow,  but 
strong  heat,  as  long  as,  possible,  in  the  heap,  without  wasting  fuel. 
By  this  means,  as  much  as  possible  of  the  sulphur  contained  in  the 
coal  will  be  expelled.  If  the  ground  where  the  heap  is  piled  is 
somewhat  moist,  the  hot  steam  arising  from  the  ground  will  carry 
off  a  large  portion  of  the  sulphur  in  the  form  of  sulphurous  acid, 


FUEL.  121 

in  case  the  heat  is  not  too  great,  and  there  is  bat  little  access  of 
atmospheric  air.  If  the  heat  is  too  great,  and  if  there  is  too  great 
an  access  of  the  air,  this  conversion  of  the  sulphur  does  not  take 
place,  and  the  sulphur  remains  in  the  coal.  The  same  circumstance 
happens  if  the  chimney  is  closed,  and  no  circulation  of  air  or  steam 
thereby  possible.  Coking  in  heaps  furnishes  generally  a  strong 
coarse  coke,  but  not  so  free  of  hydrogen  and  sulphur  as  that  fur- 
nished by  the  following  arrangement.  The  mass  of  coal  is  gene- 
rally too  large  to  permit  the  necessary  circulation  and  contact  of 
watery  vapors.  This  is  doubtless  the  cause  of  the  inferiority  of 
the  coke. 

b.  Coking  in  rows,  or  long  heaps,  is  a  preferable  mode  of  mak- 
ing coke;  these  rows  are  sometimes  one  hundred  feet  long,  seven 
or  eight  feet  wide,  and  three  feet  high.  To  coke  in  rows,  a  yard 
is  to  be  leveled  sufficiently  large  to  hold  as  much  coal  as  is  re- 
quired to  keep  the  furnaces  in  operation.  Along,  or  all  around,  this 
yard,  it  is  advisable  to  have  a  ditch  dug,  which  will  hold  a  regular 
supply  of  water  throughout  the  year;  this  water  ought  not  to  fail 
during  the  driest  seasons.  A  row  is  started  at  that  end  of  the  yard 
most  convenient  for  the  transportation  of  the  raw  coal,  and  directed 
in  a  straight  line  towards  a  point  on  the  opposite  side  of  the  yard. 
Should  there  be  a  deep  covering  of  coke  dust  all  over  the  yard,  a 
kind  of  ditch,  as  broad  as  the  coal  pile  is  designed  to  be,  may  be  pre- 
pared by  scraping  the  dust  from  the  middle,  and  drawing  it  towards 
the  spaces  between  the  rows.  This  ditch  will  indicate  the  direction 
in  which  the  coal  is  to  be  laid,  and  will  bring  it  close  to  the  moist 
ground.  The  scraped  coke  dust  is  afterwards  used  for  covering  the 
heap.  The  coal  is  arranged  as  in  the  above  case.  Due  attention 
should  be  paid  to  placing  air-channels,  or  draft-holes,  at  the  bottom, 
and  to  throwing  the  coarse  coal  in  the  centre.  At  a  distance  of 
seven  or  eight  feet  from  each  other,  tapered  posts,  seven  or  eight 
inches  in  diameter,  are  fastened  in  the  ground,  around  which 
the  coarsest  coal  is  arranged.  These  posts  or  poles  are  removed 
before  the  heap  is  fired,  and  are  designed  to  form  chimneys,  for 
the  free  vent  of  gaseous  matter,  and  the  increase  of  draft.  When 
the  pile  extends  twenty  feet,  or  more,  and  it  is  covered  with 
small  coal,  slag,  or  coke  dust,  fire  may  be  put  to  the  heap  at  different 
places  near  the  air-holes ;  and  the  row  may  then  be  continued.  In  this 
way,  it  will  happen  that  coke  is  drawn  at  one  end  of  a  row,  and  coal 
is  set  at  the  other.  After  fire  is  kindled,  and  the  heat  extended  to 
the  centre,  the  pile  may  be  covered  more  closely,  with  due  attention 


322  MANUFACTURE   OF   IRON. 

to  leaving  some  air-holes  near  the  top  ;  and  in  case  these  holes  are 
shut  by  the  expansion  of  the  coal,  they  should  be  re-opened  by  means 
of  iron  bars  run  down  to  the  centre  of  the  pile,  or  at  least  to  the 
fire.  When  the  white  flames  of  carburetted  hydrogen  cease  to  be 
visible,  the  heap  and  air-holes  may  be  closely  covered  by  coke 
dust,  and  the  coke  left  to  cool.  This  method  of  making  coke  for 
the  blast  furnace  has,  thus  far,  been  preferred  to  any  other  method. 
For  this  preference,  the  following  reasons  may  be  assigned :  the 
small  body  of  coal  on  fire  at  one  time  ;  the  large  surface  of  ground 
it  covers,  thus  presenting  unequaled  facilities  for  the  circulation  of 
watery  vapors  through  the  hot  coke ;  and  the  chance  which  it 
affords  of  retaining  the  heat  till  the  advantages  of  steam  are  pro- 
duced. For  these  reasons,  a  water  ditch  around  a  coke  yard  is  re- 
quired to  keep  the  ground  moist;  besides,  water  is  frequently  needed 
to  choke  the  fire  where  it  continues  too  long  in  the  heap,  and  thus  to 
drive  the  steam  through  the  hot  coke.  For  the  same  reason,  a  yard 
does  not  make  good  coke  if  it  is  covered  too  thickly  with  coke  dust. 

Thus  far,  the  making  of  coke  is  accompanied  with  no  difficulties ; 
still,  some  rules  require  attention,  if  we  expect  both  the  quantity  and 
quality  of  our  work  to  prove  satisfactory.  In  some  cases,  the  fire 
should  be  suffered  to  play  through  the  whole  heap  before  it  is  covered 
with  dust.  This  applies  particularly  to  slag,  small  coal,  and  to  very 
bituminous  coal,  as  well  as  to  the  whole  of  the  western  coal  fields ; 
for,  if  the  coal  is  apt  greatly  to  swell,  it  will  very  likely  choke  the 
fire.  In  setting  the  heaps,  too  much  attention  cannot  be  paid  to 
placing  the  coal  inside  in  as  open  a  manner  as  possible.  The  more 
the  coal  is  inclined  to  swell,  or,  what  is  the  same,  the  more  bitumen 
the  coal  contains,  the  more  carefully  should  this  direction  be  fol- 
lowed. The  coarse  coal  and  lumps  are  to  be  set  edgewise  ;  that  is, 
the  direction  of  the  cleavage  is  to  be  vertical,  or,  what  is  the  same 
thing,  directly  contrary  to  its  natural  position  in  the  vein.  If  the 
coal  is  dry,  if  it  is  not  very  bituminous,  fire  may  be  kindled  in  the 
chimneys  after  the  poles  are  removed  ;  but  where  it  is  bituminous, 
such  an  arrangement  would  disturb  the  draft.  Where  small  or 
very  bituminous  coal  is  to  be  coked,  it  may  be  advisable,  in  some 
cases,  to  erect,  in  the  centre  of  the  row,  chimneys  of  brick,  distant 
from  each  other  five  or  six  feet,  and  to  leave  only  draft-holes  at  the 
base,  because  such  coal  is  very  apt  to  burn  outside  or  at  the  sur- 
face, while  the  bottom  part  and  interior  are  left  unburnt. 

c.  Coking  in  Ovens. — Cases  may  occur  where  coking  in  ovens  may 
be  permitted,  even  for  blast  furnace  coke;  as,  for  instance,  where  a 


FUEL. 


123 


very  brittle  coal,  but  free  of  sulphur,  is  to  be  charred.  But  these 
cases  are  rare,  at  least  in  the  coal  fields  at  present  worked;  for  all 
our  coal,  when  compared  to  that  employed  in  the  blast  furnaces 
in  Europe,  may  be  considered  more  or  less  sulphurous.  However 
that  may  be,  coke  ovens  are  practicable ;  at  least,  they  are  at  pre- 
sent in  general  use  in  the  Pittsburgh  coal  fields.  All  the  coke  used 
in  cupola  ovens  and  refining  fires  in  the  Western  States  is  made  in 
ovens.  Coke  ovens  of  various  forms  have  been  erected,  sometimes 
with  regard  to  quality,  but  most  generally  to  quantity ;  and  for  the 
latter  purpose  they  have  been  brought  to  great  perfection.  In  our 
case,  quantity  is  of  secondary  consideration  ;  the  obtaining  of  coke, 
free  of  bitumen  and  sulphur,  is  the  object  at  which  we  aim.  All 
the  various  coke  ovens  are  constructed  mainly  upon  one  principle ; 
that  is,  they  are  built  in  the  form  of  a  common  bake  oven,  and 
generally  of  capacity  sufficient  to  receive  a  charge  of  two  or  three 
tons  of  coal  at  once.  Some  are  round;  others  egg-shaped  ;  and  at 
the  Clyde  Iron  Works,  in  Scotland,  the  hearth  is  square.  "  Ures 
Dictionary  of  Arts  and  Manufactures"  contains  a  description  of  an 
excellent  arrangement  for  coking  coal,  erected  for  the  use  of  the  loco- 
motive engines  of  the  London  and  Birmingham  Railway  Company; 
but  we  doubt  the  utility  of  such  ovens  in  iron  establishments,  for  we 
cannot  believe  that  the  large  quantity  of  coke  yielded  is  of  quality  suf- 
ficiently good  for  the  manufacture  of  iron.  In  Germany  and  France, 
coke  ovens  have  been  built  of  admirable  construction,  as  far  as  the 
saving  of  fuel  is  concerned;  but  iron  masters  who  require  a  good 
article,  burn  coke  in  the  open  air.  Of  the  different  forms  of  coke 
ovens,  we  should  prefer  the  most  simple ;  such  a  form  is  at  present 

Fig.  34. 


Front  elevation  of  a  Pittsburgh  coke  oven. 


124 


MANUFACTURE   OF  IRON. 


in  general  use  in  the  neighborhood  of  Pittsburgh ;  the  form  and  di- 
mensions of  such  an  apparatus  are  exhibited  in  the  following  figures. 
Fig.  34  represents  a  double  coke  oven,  in  front  view,  built  of  stone 
or  common  brick,  against  the  slope  of  a  hill,  so  that  the  coal  may 
be  unloaded  on  the  top  of  the  oven ;  it  is  accessible  by  railroad,  or 
common  carts  or  wagons.  Fig.  35  is  the  ground-plan  of  the  twin 

Fig.  35. 


Ground-plan  of  a  Pittsburgh  double  coke  oven. 

oven ;  it  shows  the  laying  out  of  the  hearth,  which  is  ten  feet  long, 
and  ten  feet  wide,  with  corners  rounded,  so  as  to  prevent  the  coke 
sticking  in  them.  Fig.  36  shows  a  cross  section  of  one  oven  in 
the  direction  of  A,  B,  Fig.  35.  The  same  letters  are  used  to  desig- 
nate the  same  objects  in  the  different  figures,  a,  a  represent  doors, 
two  feet  in  width,  designed  to  be  shut  with  brick  and  clay  when 

Fig.  36. 


Section  of  a  Pittsburgh  coke  oven. 

the  oven  is  to  be  filled  with  coal.  Some  openings  are  left  in  the 
temporary  brick  work  of  the  door,  to  regulate  the  fire  ;  but  these  are 
to  be  shut  when  the  fire  has  penetrated  through  the  mass  of  coal. 
by  b  are  iron  hooks,  walled  in,  into  which  an  iron  bar  from  an  inch 
to  an  inch  and  a  half  square  is  placed;  this  bar  serves  to  strengthen 
the  temporary  brick  filling  in  the  door,  and  to  prevent  the  throwing 


FUEL.  125 

out  by  the  swelling  of  the  coal :  e,  Fig.  36,  is  a  round  hole,  left  in 
the  top,  through  which  the  disengaged  gases  may  escape  ;  this  hole, 
from  twenty  to  twenty-four  inches  in  diameter,  is  left  open  until  all 
the  bitumen  of  the  coal  is  driven  off,  after  which  it  is  to  be  shut  by  a 
cast  iron  plate,  and  luted  with  clay.  The  interior  of  the  furnace 
is  to  be  built  with  fire  brick  and  fire  clay  mortar ;  the  rough  wall 
either  with  stones  or  common  brick.  Such  an  oven  has  a  capacity  of 
from  seventy-five  to  eighty  bushels ;  it  will  furnish  from  Pittsburgh 
slag  coal  nearly  one  hundred  bushels  of  coke.  After  it  is  finished 
by  the  masons,  and  ready  for  use,  some  wood  is  thrown  on  the 
hearth  towards  the  door,  which  is  to  be  repeated  each  time  the  oven 
gets  cold ;  the  door  is  then  walled  up ;  and  the  coal  thrown  in 
through  the  hole  at  the  top,  and  spread  uniformly  over  the  hearth. 
Eighty  bushels  of  coal  will  cover  the  bottom  about  twelve  inches 
high,  which  will  rise  to  fifteen  inches  after  being  burnt.  The  top 
arch,  therefore,  should  be  sufficiently  high  from  the  bottom  to  per- 
mit the  swelling  of  the  coal,  and  the  breaking  up  of  the  solid  mass 
of  coke.  The  height  of  the  arch  from  the  bottom  is  generally  from 
twenty  to  twenty-four  inches ;  in  the  centre,  thirty  inches.  When 
the  coal  is  properly  spread,  fire  may  be  applied  at  the  door  and  top  ; 
after  the  first  and  second  heats,  it  needs  no  kindling,  for  the  bottom 
and  sides  of  the  oven  are  sufficiently  warm  to  kindle  the  coal.  After 
ten  or  twelve  hours,  the  bituminous  gases  are  mostly  expelled;  the  top 
can  then  be  closed,  that  the  oven  may  cool ;  eight  or  ten  hours  will 
be  sufficient  for  this  purpose.  Though  the  coke  may  be  red  hot, 
there  is  no  danger  of  its  further  burning.  The  door  is  now  opened,  and 
the  hot  coke  removed  in  iron  wheelbarrows.  This  is  frequently  quite 
a  hard  task ;  and  a  set  of  long  and  strong  crowbars,  besides  some 
long  iron  scrapers,  are  needed  in  every  establishment  of  this  kind, 
to  facilitate  operations,  and  to  prevent  any  delay  of  the  regular 
work.  The  coke  of  the  first  heat  is  generally  raw  at  the  bottom, 
and  spongy  at  the  top  ;  but  the  second  and  following  heats  im- 
prove as  the  oven  gets  hotter.  We  may  say,  generally,  the  hotter 
the  oven,  the  better  the  coke.  Good  coke  ought  to  exhibit  a  uni- 
form crystalline  texture  throughout  the  whole  mass,  and  when  cold, 
should  sound  like  fragments  of  stoneware. 

One  of  the  most  common  arrangements  of  coke  ovens,  in  the  Old 
World,  is  exhibited  by  the  following  diagrams:  Figs.  37  and  38. 
The  oven  here  represented  is  that  of  the  Northumberland  and 
Lemington  Iron  Works  upon  Tyne.  Four  ovens  are  shown  to  be 
in  a  line ;  this  arrangement  is  preferred  because  it  keeps  the  heat 


126  MANUFACTURE   OF   IRON. 

together,  and  saves  masonry.  The  hearth  of  the  oven  is  an  oblong 
square,  ten  by  twelve  feet ;  and  from  the  bottom  to  the  arch  is  three 
feet  high.  The  rough  walls  are  of  common  brick,  two  feet  thick, 


o 

Fig.  37. 


English  coke  ovens. 

and  the  lining  of  fire  brick.  At  the  centre,  on  the  top,  is  a  round 
hole,  two  and  a  half  feet  in  diameter,  through  which  gases  escape. 
The  doors  are  three  feet  square.  On  the  top  is  a  cast  iron  frame, 
with  two  rips ;  between  these  rips  a  door  slides.  This  door  is  of 
wrought  iron,  filled  with  brickwork,  which,  sliding  upon  the  above 
frame,  may  cover  the  gas  hole,  or  be  withdrawn  at  pleasure.  The 
same  arrangement  is  used  to  shut  the  doors,  with  this  difference, 

Fig  38. 


Ground-plan  of  English  coke  ovens. 

that  the  door  is  vertical,  and  balanced  by  a  lever.  In  the  brick 
filling  of  the  door,  are  a  number  of  draft-holes,  through  which  air 
can  have  access  to  the  burning  coal. 

This  arrangement,  in  its  principle,  differs  not  in  the  least  from 
the  Pittsburgh  arrangement.  But  the  execution  of  the  latter  is 
more  perfect  than  that  of  the  former,  though,  at  the  same  time,  more 
expensive,  and  less  suited  to  our  country.  This  oven  is  charged 
with  from  two  to  three  tons  of  coal.  The  manipulations  are  the 
same  as  those  at  the  Pittsburgh  ovens.  In  countries,  Germany  and 
France,  for  instance,  where  coal  tar  is  of  value,  and  its  gathering 
yields  profit,  coke  ovens  have  a  different  form.  As  coal  tar  may  be 


FUEL. 


127 


highly  valuable  in  some  parts  of  the  United  States,  we  shall  de- 
scribe, one  of  these  ovens.     Fig.  39  represents  a  cross  section  of  a 

Fig.  39. 


German  coke  oven,  for  gathering  coal  tar. 

coke  oven  which,  for  many  years,  has  been  in  operation  in  Silesia, 
eastern  Germany,  and  may  be  considered  of  an  approved  form. 
This  oven  is  about  nine  feet  high ;  it  is  of  a  cylindrical  form,  and 
is  four  feet  in  diameter ;  the  interior  is  built  of  fire  brick,  and  the 
exterior  of  common  brick  or  stones,  bound  with  iron  hoops.  The 
coal  is  put  in  partly  through  the  door  a,  and  partly  through  the  top 
hole  b.  Care  is  taken  to  lay  coarse  coal  at  the  bottom.  The  bot- 
tom part  of  the  oven  forms  a  kind  of  grate,  for  the  holes  <?,  <?,  c  are 
left  open,  in  which  iron  pipes  are  walled  in ;  there  are  seven  of 
such  holes  in  the  bottom,  jffhe  holes  in  the  side  wall  c?,  c?,  d  are 
draft-holes,  secured  by  iron  pipes.  The  top  is  covered  with  an  iron 
plate,  in  which  the  lid  e  fits.  The  tar  and  gases  are  conveyed  by 
the  iron  pipe  /,  into  a  reservoir,  or  tar  barrels.  This  pipe  is  con- 
ducted through  cold  water,  that  the  tar,  during  summer,  may  con- 
dense ;  but  in  winter,  the  atmospheric  air  is  sufficiently  cool  to  con- 


128  MANUFACTURE   OF   IRON. 

dense  all  the  tar  which  escapes  from  the  oven.  Coarse  coal  is  put 
in  the  bottom  part;  upon  this  is  thrown  slack  coal.  If  the  oven  is 
about  two-thirds  filled,  fire  is  kindled,  and  the  door  a  shut  with  brick 
and  clay  mortar.  The  fire  may  be  safely  left  to  burn,  and  the  top 
plate  e  may  be  put  on,  and  luted  with  clay.  After  eight  or  ten 
hours,  the  upper  row  of  holes  d  will  appear  brightly  red,  and  may 
be  shut.  After  that  time  has  again  elapsed,  the  second  row  from 
above  may  be  shut.  Twelve  hours  more  may  elapse,  when  the 
lower  holes,  becoming  bright,  may  be  closed.  By  this  time,  tar 
almost  ceases  to  be  produced.  Then,  after  shutting  carefully  all 
the  holes,  the  oven  may  be  left  to  cool.  This  cooling  will  take  place 
in  the  course  of  the  next  twelve  hours. 

The  charge  in  such  an  oven  amounts  to  two  tons  of  coal.  Two 
charges  may  be  made  during  one  week,  if  the  coke  is  drawn  in 
time.  The  coke  thus  produced  is  very  hard  and  compact,  and 
may  be  considered  superior  to  any  other;  but  the  manipulations  in 
this  oven  are  both  expensive  and  troublesome.  One  bushel  of  coal 
furnishes  three-fourths  of  a  bushel  of  coke ;  and  one  hundred  pounds 
of  coal  produce  fifty-three  pomids  of  coke,  and  five  gallons  of  tar. 
The  bituminous  coal  of  upper  Silesia  is  referred  to.  One  hundred 
pounds  of  this  coal  furnish  from  forty-five  to  forty-seven  pounds  of 
coke,  when  burnt  in  the  open  air;  while  one  bushel  of  coal  furnishes 
nearly  one  bushel  and  a  quarter  of  coke. 

In  the  neighborhood  of  St.  Etienne,  in  France,  a  kind  of  double 
coke  oven  is  in  use,  which  is  worthy  of  notice.  Its  form  is,  in  the 
main,  the  same  as  that  of  any  other  coke  oven,  but  differs  in  being 
of  larger  dimensions,  and  in  having  two  doors  for  drawing,  instead, 
like  other  ovens,  of  but  one. 

Fig.  40. 


French  coke  oven. 


Fig.  40  represents  a  double  oven;  a,  a  are  two  opposite  doors. 
The  bottom  is  formed  of  hard  rammed  fire  clay;  its  top  and  sides 
are  of  fire  brick ;  the  rough  wall  either  of  common  bricks  or  stones. 


FUEL.  129 

The  chimney  5  is  eighteen  inches  in  diameter,  and  the  whole  arch 
is  covered  with  sand,  to  keep  in  the  heat.  Its  arrangements,  in  other 
respects,  are  the  same  as  those  of  other  coke  ovens.  It  contains  a 
charge  of  from  three  to  four  tons  of  coal.  The  hearth  ought  to  be 
sufficiently  large  to  take  this  amount  of  coal,  piled  ten  inches  high. 
The  centre  of  the  arch  may  be  four  feet  from  the  bottom. 

d.  Coking  in  Iron  Retorts. — By  the  distillation  of  coal  in  iron 
retorts,  no  coke  can  be  made  serviceable  for  the  manufacture  of 
iron.  Coke  thus  made  is  always  light,  spongy,  and  never  free  from 
bitumen  or  sulphur  ;  qualities  which  render  it  unfit  for  an  iron 
manufactory.  We  shall,  therefore,  dispense  with  the  consideration 
of  this  method. 

IX.  G-eneral  Remarks  on  Coking. 

The  making  of  good  coke  is,  to  the  manufacturer  of  iron,  a  very 
difficult  task.  Good  coke  ought  to  be  silvery  white  and  compact ; 
it  ought  to  sound  like  good  crockery  ware,  and  should  be  free  of 
bitumen,  hydrogen,  and  sulphur.  Good  color  and  compactness  may 
be  secured  in  various  ways ;  but  the  other  qualities  are  not  so  easily 
secured.  Hard,  compact  coke  will  be  obtained  from  large  piles, 
either  in  ovens  or  in  the  free  air,  if  the  fire  is  brisk  and  the  cover- 
ing heavy ;  but  coke  made  in  that  way  always  contains  more  sul- 
phur and  hydrogen  than  it  should  contain.  A  large  body  of  coal, 
under  a  slow  fire,  furnishes  light  spongy  coke,  but  more  free  of  sul- 
phur and  bitumen  than  under  a  quick  fire.  A  medium  heat  serves 
better  than  either  extreme.  Where  the  body  of  coal  is  kindled,  the 
heat  ought  to  be  kept  as  low  as  possible ;  the  longer  the  heat  is 
applied,  the  better  will  be  the  result.  By  this  means  most  of  the 
sulphur,  as  well  as  the  hydrogen,  will  be  expelled.  When  we  have 
ascertained  that  no  more  sulphur  escapes,  the  heat  may  be  raised 
by  giving  free  vent  to  the  gases  through  the  air-holes.  If  a  cur- 
rent of  steam  can  possibly  be  passed  through  the  glowing  coal,  dur- 
ing the  first  stages  of  coking,  it  should  be  done.  In  the  yard, 
where  we  coke  in  piles,  this  may  be  easily  effected,  by  keeping 
the  ground  moist,  and  laying  the  coal  as  closely  as  possible  upon 
it.  But  in  ovens  this  is  more  difficult,  because  in  them  it  is  not 
so  convenient  to  change  and  regulate  the  fire. 

If  the  bottom  of  the  ovens  is  made  of  clay  laid  upon  sand,  and 
if  we  are  able  to  regulate  the  moisture  of  this  sand,  a  great  deal 
may  be  effected.     In  this  manner  the  French  oven,  Fig.  40,  is  con- 
structed.    This  is  the  only  practicable  method  by  which  watery 
9 


130  MANUFACTURE   OF  IRON. 

vapors  can  be  made  to  pass  through  the  hot  coal — a  matter  requiring 
attention  in  the  first  stages  of  the  operation.  If  the  hydrogen  is 
expelled  by  a  too  lively  heat  at  the  commencement  of  the  operation, 
the  sulphur  is  very  apt  to  remain,  and  cannot  be  driven  off ;  for  car- 
bon and  sulphur,  combined  by  strong  heat,  cannot  be  separated, 
except  by  their  mutual  destruction.  We  cannot  pay  too  much 
attention  to  this  subject,  for  upon  it  depends  the  success  of  the  blast 
furnace  operation.  Sulphurous  coal,  by  improper  treatment,  will 
produce  sulphurous  coke,  and  consequently  sulphurous  metal,  which, 
in  all  subsequent  manipulations,  will  be  injurious,  troublesome,  and 
expensive.  By  sprinkling  a  little  water  over  red-hot  coke,  drawn 
freshly  from  the  oven  or  pile,  we  may  ascertain  whether  it  contains 
sulphur.  If  the  odor  of  sulphuretted  hydrogen,  or  rotten  eggs,  is 
emitted,  the  presence  of  sulphur  is  indicated.  If  the  hot  and 
melted  iron  in  the  pig  bed. throws  off  sulphur,  the  coking  of  the 
coal  requires  our  closest  examination.  In  some  establishments, 
workmen  have  been  advised  to  sprinkle  water  over  the  red-hot 
coke,  which  may  be  done  from  the  nose  of  a  watering-pot,  partly 
with  the  object  of  expelling  the  remaining  sulphur,  and  partly  with 
the  object  of  extinguishing  the  fire.  This  is  a  bad  habit ;  it  injures 
the  coke,  makes  it  rotten,  and  seriously  impairs  its  utility  in  the 
blast  furnace. 

The  yield  of  coke  varies  according  to  differences  in  coal.  In 
England,  seventy-five  per  cent,  by  weight,  and  120  by  measure,  is 
considered  a  good  average  yield.  On  the  Continent,  coal  varies 
greatly.  That  which  is  very  bituminous  yields  fifty-five  per  cent, 
weight  in  ovens ;  and  from  coal  less  bituminous,  the  yield  varies 
from  sixty  to  seventy-five  per  cent.  Professor  Johnson,  of  Phila- 
delphia, in  his  "  Report  to  the  Navy  Department  of  the  United 
States  on  American  Goals"  has  given  us  some  highly  useful  notes 

on  the  amount  of  coke  produced  from  different  kinds  of  American 

coal.     We  extract  the  following  data  : — 

A  specimen   of  the  Cumberland,  Maryland,  coal,   thick  vein, 

gave,  by  slow  coking,  seventy-eight  per  cent,  of  coke ;  by  rapid 

application  of  heat,  but  seventy-two  per  cent.     The  thick  vein  of 

Cumberland  or  Frostburg  is  not  very  bituminous. 

Coal  fromBlossburg,Tioga  county,  Pa.,  gave  eighty-three  per  cent. 
Coal  from  Ralston,  Lycoming  county,  Pa.,  gave  eighty-six  per 

cent.     This  appears  to  be  a  good  quality  of  coal ;  because  but 

little  sulphur  has  been  found  in  it. 

Coal  from  Karthaus,  Clearfield  county,  Pa.,  yielded  eighty-eight 

per  cent,  of  coke. 


FUEL.  131 

Coal  from  Summit  Portage  railroad,  Cambridge  county,  Pa.,  gave 
seventy-nine  per  cent.  This  coal  is  very  sulphurous,  and  contains 
upwards  of  10  per  cent,  ashes. 

Coal  from  the  Deep  Run  mines,  near  Richmond,  Virginia,  yielded 
eighty  per  cent,  of  coke ;  but  it  contains  upwards  of  eleven  per  cent, 
of  ashes. 

Coal  from  Henrico  county,  Virginia,  gave  seventy-five  per  cent, 
of  coke.  It  appears  to  be  a  good  coal  for  the  manufacture  of  iron. 
It  contains  scarcely  any  sulphur,  and  very  little  ashes. 

Coal  from  the  Creek  Coal  Company,  Chesterfield  county,  Vir- 
ginia, yielded  sixty-eight  per  cent,  of  coke. 

Coal  from  Clover  Hill  mines,  Appomatox  River,  Virginia,  yield- 
ed sixty-eight  per  cent,  of  coke ;  and  it  appears  to  be  well  adapted 
for  the  manufacture  of  iron. 

Coal  from  Midlothian  Coal  Company,  Virginia,  gave  sixty- six 
per  cent,  of  coke.  This  is  also  suitable  for  the  manufacture  of  iron. 

Coal  from  Petersburgh,  Virginia,  resembles  the  Clover  Hill  coal, 
and  is  of  about  the  same  quality. 

Coal  from  Nova  Scotia  yielded  sixty-two  per  cent,  of  coke;  but 
it  is  very  sulphurous,  and,  unless  great  attention  is  paid  to  coking,  it 
is  unfit  for  use  in  the  blast  furnace.  Pictou  coal  appears  to  be  of 
better  quality. 

Coal  from  Cannelton,  Indiana,  yielded  sixty-four  per  cent,  of 
coke;  not  much  ashes  or  sulphur. 

Coal  from  Pittsburgh,  Pa.,  produced  sixty-eight  per  cent,  of 
coke ;  hardly  any  sulphur,  and  little  ashes. 

Coal  from  Wheeling,  Va.,  yielded  fifty-seven  per  cent,  of  coke; 
earthy  matter  3.9,  and  rather  more  sulphur  than  the  Pittsburgh 
coal.  Its  coke,  as  well  as  that  from  the  Pittsburgh  coal,  is  an  ex- 
cellent article  for  the  manufacture  of  iron. 

Coal  from  Missouri  yielded  fifty-seven  per  cent,  of  coke  ;  scarce- 
ly any  earthy  matter,  and  but  little  sulphur. 

Coals  of  inferior  quality,  or  those  whose  composition  prevents 
their  application  in  the  blast  furnace,  we  have  forborne  to  notice. 
It  is  to  be  regretted  that  a  great  variety  of  coal  from  our  large 
western  coal  fields  was  not  sent  to  Mr.  Johnson.  A  good  oppor- 
tunity of  testing  the  relative  value  of  that  coal  was  thus  lost.  All 
the  above  experiments  of  coking  were  made  in  a  closed  vessel. 
The  yield  in  coke  ovens,  or  in  the  open  air,  is  not  so  large.  The 
coal  of  the  "Western  States  is  generally  of  good  quality;  particular- 
ly the  veins  lying  above  the  extensive  Pittsburgh  vein.  The  lower 
veins  do  not  yield  so  good  an  article  for  the  blast  furnace. 


132 


MANUFACTURE   OF   IRON. 


Highly  bituminous  coal  loses,  on  an  average,  from  fifty  to  fifty-five 
per  cent. ;  coal  that  is  drier,  from  thirty  to  forty  per  cent.,  by  being 
coked  in  stacks  or  heaps.  Coked  in  ovens,  the  same  coal  will 
respectively  lose  from  forty  to  forty-five  and  from  twenty  to  thirty 
per  cent. ;  that  is,  twelve  per  cent,  more  coke  will  be  yielded  in 
ovens  than  in  heaps,  or  in  the  open  air.  Retorts,  or  closed  vessels, 
furnish  a  still  larger  result  than  ovens. 

X.  Heat  liberated  by  Fuel. 

The  term  "heat  is  used  to  denote  a  state  or  condition  of  a  body 
which  produces  a  specific  sensation  which  all  immediately  recog- 
nize. The  effects  of  heat,  and  its  generation  and  liberation,  are 
all  with  which  we  are  at  present  concerned.  Heat  is  generated, 
or,  properly  speaking,  liberated,  by  almost  every  chemical  process ; 
at  least,  by  all  those  processes  by  which  simple  elements  com- 
bine to  form  compounds.  For  instance,  heat  is  liberated  when 
oxygen,  sulphur,  and  chlorine  combine  with  the  metals,  or  with 
carbon  and  hydrogen ;  or  when  each  combines  with  the  other. 
A  knowledge  of  the  amount  (quantity),  as  well  as  of  the  degree 
or  temperature  (quality),  of  heat,  liberated  during  the  process  of 
combustion,  and  in  various  chemical  actions  ;  and  an  acquaintance, 
especially,  with  the  heat  liberated  by  destruction  of  fuel,  are,  to 
the  enlightened  iron  manufacturer,  absolutely  necessary. 

a.  The  quantity  of  heat  liberated  from  fuel  varies  in  different 
compounds ;  but  it  may  be  laid  down  as  a  rule,  that  the  amount  of 
heat  is  in  a  constant  ratio  to  the  amount  of  oxygen  consumed  by 
any  given  process,  provided  the  oxidation  is  carried  to  the  proper 
degree.  A  practical  elucidation  of  this  subject  we  shall  presently 
furnish.  We  shall  give  first  a  series  of  theoretical  experiments  by 
which  the  amount  of  heat  liberated,  and  therefore  the  difference,  or 
relative  value,  of  fuel  may  be  estimated.  In  these  experiments,  the 
relative  value  of  wood  and  other  fuel  is  estimated  by  weight : — 

ANALYSIS  OF  RELATIYE  VALUE  OF  FUEL. 


Per  cent. 

Linden,  air-dried  -  34 

"       dried  artificially  38 

"         "         "       strongly  40 

Beech,  air-dried     -  33 

"       dried  artificially  36 

Oak,  air-dried                  -  29 

"    dried  artificially    -  30 

Sugar  maple  "       "       -  36 


Per  cent. 

Ash,  air-dried  -  30 

"  dried  artificially  -  33 
"  «  «"  strongly  35 

Pine,  air-dried  -  30 

"  dried  artificially  -  33 

Poplar,  air-dried  -  34 

"  dried  artificially  3T 


FUEL. 


133 


ANOTHER   ANALYSIS. 


Per  cent. 

-  31 

-  39 

-  33 

-  39 

-  32 
"          "      dried  artificially  40 

Beech,  air-dried  -     31 

"       dried  artificially      -     39 


Oak,  air-dried  - 
"  dried  artificially 

Ash,  air-dried  - 
"  dried  artificially 

Sugar  maple,  air-dried 


Birch,  air-dried 

"      dried  artificially 
Poplar,  air-dried 

"        dried  artificially 
Linden,  air-dried 

dried  artificially 
Pine,  air-dried 

"     dried  artificially 


Per  cent. 

-  31 
-  39 

-  29 

-  40 

-  32 

-  41 

-  31 

-  40 


VALUE   OF   CHARCOAL. 


Poplar,  maple,  ash,  average  68  per  cent. ;  charcoal  from  other 
species  differs  but  slightly. 


VALUE   OF   TURF. 

French  specimen 
German      " 
Irish  " 

VALUE   OF   TURF   CHARCOAL. 

French  specimen 

VALUE   OF   BROWN   COAL. 

French  specimen 

German      "  - 

Grecian      "  - 


Per  cent. 

18  to  34 
26  "  42 
28  "  62 

40  to  58 

36  to  57 

41  "  58 
36  "  52 


VALUE    OF   STONE    COAL. 


Dowlais,  Wales 
Germany  - 

Newcastle,  England  - 
France,  Grande  Croix 
Spain,  Asturian 
France,  St.  Etienne  - 
Cherry  coal,  Derbyshire, 
England 


Coke  from  France     - 

"       "     the  Gas  Works,  Paris 
"       "     Germany 


Per  cent.                                                           Per  cent. 

- 

72 

Cannel  coal,  Glasgow, 

- 

70 

Scotland 

56 

- 

70 

Cannel  coal,  Lancashire, 

- 

67 

England 

53 

- 

59 

Germany,  Silesia 

48 

- 

57 

Austria,  Lower  Danube 

43 

Durham,  England 

71 

- 

61 

VALUE   OF  COKE. 

Per  cent. 

65 
50 
64 


134 


MANUFACTURE   OF   IRON. 


VALUE  OF  ANTHRACITE. 

Per  cent. 

Pennsylvania    -  71 

France  69 

Savoy  -  -         60 

The  preceding  tables  are  of  European  origin,  and  as  they  have 
been  mostly  drawn  up  by  Berthier,  they  may  be  relied  upon  as 
correct.  We  shall  still  further  elucidate  this  subject  by  present- 
ing some  of  the  observations  of  Professor  Johnson  : — 

American  Coal,  and  the  Evaporative  Power  of  American  Fuel. 


£ 

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III 

Anthracite. 

Beaver  Meadow,  Pa.   - 

1.6 

2.38 

88.9 

7.11 

10.4 

66.8 

Forest  Improvement,  Pa.     - 

1.4 

3.07 

90.7 

4.41 

10.8 

69.4 

1.5 

5.28 

89.1 

5.56 

9.6 

61.7 

Lakawana,  Pa.    -         -         -         - 

1.4 

3.91 

87.7 

9.25 

10.7 

68.8 

Coke. 

Midlothian,  Va.    - 

16.55 

10.3 

66.2 

Cumberland,  Md.         ... 

13.34 

10.3 

66.2 

"             Mining  Company,  Md. 

12.40 

11.2 

72.0 

Bituminous  Coal. 

Maryland  Mining  Company,  Md. 

1.4 

12.31 

73.5 

12.40 

11.2 

72.0 

Cumberland,  Md.         ... 

1.3 

15.52 

74.29 

9.30 

11.0 

70.7 

Blossburg,  Pa.      .... 

1.3 

14.78 

73.41 

10.77 

10.9 

70.0 

Karthaus,  Pa.       .... 

1.2 

19.53 

73.77 

7.0 

9.8 

63.0 

Cambria  Co  ,  Pa.           ... 

1.4 

20.52 

69.37 

9.15 

10.2 

65.5 

Clover  Hill,  Va.           ... 

1.2 

32.21 

56.83 

10.43 

8.5 

54.6 

Tippecanoe,  Va.           ... 

1.3 

34.54 

64.62 

9.37 

8.5 

54.6 

Pictou,  Nova  Scotia      ... 

1.3 

27.83 

65.98 

13.39 

9.7 

62.3 

Liverpool    

1.2 

39.69 

54.90 

4.62 

8.2 

52.7 

Scotch          

1.5 

39.19 

48.81 

9.34 

7.7 

49.6 

Pittsburgh,  Pa.     - 

1.2 

36.76 

54.97 

7.07 

8.9 

57.2 

Dry  pine  wood   -         ... 

0.3 

4.7 

30.2 

The  data  in  this  table  have  been  deduced  from  direct  experi- 
ments made  on  the  steam  boiler,  and  therefore  are  only  measurably 
applicable  to  our  case.  In  the  iron  manufacturing  apparatus,  heat 
is  generated  and  escapes  at  a  far  higher  temperature  than  that  of 
a  steam-boiler. 

The  above-mentioned  law,  that  the  heat,  liberated  by  combus- 
tion, is  in  direct  proportion  to  the  oxygen  consumed,  is  one  of  the 
most  useful  inculcations  of  chemistry.  By  this  law,  we  are  enabled, 
if  we  know  the  composition  of  the  fuel,  to  calculate  the  amount  of 


FUEL.  135 

heat  it  liberates.  The  composition  of  fuel  has  been  given  at  the 
proper  place.  It  is  only  necessary  to  present  here  the  formula  which 
will  enable  any  one  to  calculate  the  quantity  of  heat  evolved  by 
any  process  of  combustion.  This  law  has  been  applied  by  Berthier 
to  ascertain  the  quantity  of  heat  liberated  by  any  fuel  in  combin- 
ing with  oxygen. 

The  process  of  accomplishing  this  is  as  follows:  The  combustible, 
properly  dried,  is  pounded  into  an  impalpable  powder.  A  given 
amount  of  this  powder,  say  fifty  grains,  is  intimately  mixed  with 
forty  times  its  weight  of  litharge,  and  then  placed  in  a  good 
Hessian  crucible.  The  whole  is  to  be  covered  with  a  layer  of 
litharge,  to  prevent  the  atmospheric  air  from  penetrating  into  the 
mixture.  The  crucible  is  carefully  placed  in  an  air  furnace  or 
common  stove.  No  particles  of  coal  from  the  fire  should  be  suffered 
to  fall  into  it.  In  fifteen  or  twenty  minutes,  the  crucible  will  be 
red  hot,  and  may  be  removed  from  the  fire,  or,  what  is  still  better, 
left  until  the  litharge  on  the  top  is  in  complete  fusion.  After  cooling 
the  crucible,  we  find  at  the  bottom  a  button  of  metallic  lead.  This 
must  be  weighed,  for  it  is  the  true  standard  of  the  oxygen  consumed 
by  the  fuel.  One  part  by  weight  of  carbon  represents  2.66  parts  of 
oxygen,  which,  taken  from  litharge,  represents  34.5  parts  of  lead. 
This  amount  of  oxygen,  carbon,  or  lead,  will  heat  78.15  parts  of 
water  from  32°  to  212°;  so  that  every  unit  of  lead  represents 

78.15 

3^-5=  2.265  units  of  water,  heated  from  32°  to  212°.     One  part 

of  carbon  combines  with  2.66  oxygen  to  form  carbonic  acid;  and 
one  part  of  hydrogen  combines  with  eight  parts  of  oxygen.  If, 
from  the  sum  total  of  oxygen,  we  now  subtract  the  amount  of 
oxygen  which  the  fuel  contained,  we  shall  find  the  amount  needed 
for  combustion.  This  latter  is  the  measure  of  the  power  of  heat  of 
the  fuel.  For  example,  oak  wood  is  composed  of  0.4943  carbon, 
0.0607  hydrogen,  which  takes  0.4943  x  2.66+0.0607  x  8= 1.318  + 
0.485=1.803  oxygen;  subtract  the  oxygen  of  the  wood=  0.445, 
then  1.803  —  0.455=1.358  oxygen  is  left.  This  is  equal  to  17.58 
lead  or  39.8  water,  which  by  one  part  of  oak  wood  can  be  heated 
from  32°  to  212°.  In  this  way  the  value  of  fuel,  or  the  quantity 
of  heat  it  liberates,  may  be  very  simply  ascertained.  But  the  iron 
manufacturer  must  pay  particular  attention  also  to  the  quality  of 
heat,  of  which  we  shall  speak  hereafter.  In  accordance  with  this 
method,  the  following  experiment  has  been  made.  The  water  is 
assumed  to  be  heated  from  32°  to  212°  Fahr. 


136  MANUFACTURE   OF   IRON. 

1  pound  of  bituminous  coal  will  heat  60  pounds  of  water. 
1         "         pure  carbon  "         78  " 

1         "         charcoal  "         75  " 

1         "         dry  wood  "         36  " 

1         "         air-dried  wood          "         27  " 

1         "         turf  "         25  to  30     " 

1         "         alcohol  "         67J-  " 

1         "         oil,  wax  "         90  to  95     " 

1         "         ether  "         80  " 

1         "         hydrogen  "       236  " 

These  substances  naturally  combine  with  various  amounts  of 
oxygen.  Assuming  oxygen  to  be  one,  and  the  water  to  be  heated 
from  32°  to  212°,  then 

1  pound  of  oxygen,  combining  with  hydrogen,  will  heat  29  J  pounds. 
1         "  "  «  carbon,  "      29J      " 

1         "          «  "  alcohol,  "      28        " 

1         "  "  "  ether,  "      28        « 

b.  Quality  of  Heat.  —  When  a  combustible  combines  with  oxygen, 
that  is,  burns,  the  resulting  compound  contains  all  the  heat  liberated 
in  the  process.  From  this  compound  the  heat  is  abstracted  by  other 
substances  which  come  in  contact  with  it.  How  high  the  tempera- 
ture in  such  cases  of  combustion  will  be,  may  be  approximately 
calculated.  The  following  demonstration  is  designed  rather  to  give 
a  clear  insight  into  the  process  of  combustion  than  a  real  calcula- 
tion of  the  quality  of  heat  evolved. 

If  one  part  of  oxygen  by  weight  combines  with  hydrogen,  it 
forms  1.152  water,  or  steam  of  a  high  temperature.  If  gaseous 
water  had  the  same  capacity  for  latent  heat  as  condensed  water, 
one  pound  of  oxygen  would  raise  the  temperature  of  29J  pounds 
of  water  from  32°  to  212°,  and  the  temperature  of  the  formed 


water  would  be        '  18Q  =  32+4752°.    But  the  capacity  of  steam 
1.1.25 

for  caloric  is  only  0.8407,  therefore  less  than  water;  and  the  tem- 
perature of  steam  will  be,  in  the  moment  of  generation,  =  —  ^—  —  = 

1.19  times  higher,  or  4752  .  1.9=5654°.  Let  us  take,  instead 
of  pure  oxygen,  atmospheric  air  ;  then  23.1  parts  oxygen  are 
mixed  with  76.9  nitrogen,  if  we  neglect  the  other  compounds 
of  atmospheric  air.  The  nitrogen  absorbs  a  part  of  the  heat 
produced  by  the  forming  of  water  ;  and  as  the  capacity  of  nitrogen 


FUEL.  137 

for  caloric  is  0.2734,  or  nearly  one-third  of  that  of  steam,  the 
temperature  of  the  oxy-hydrogen  flame,  nourished  by  atmospheric 
air,  will  be  only  half  as  high  as  it  would  be  if  nourished  by  pure 
oxygen;  that  is  to  say,  76  parts  of  nitrogen  will  absorb  as  much 
heat  as  the  steam  formed  by  23  parts  of  oxygen,  because  23.1  of 
oxygen  form  25.95  water,  little  more  than  one-third  of  the  nitrogen. 
Inasmuch  as  nitrogen  has  only  one-third  the  capacity  of  steam  for 
heat,  the  temperature  will  be  reduced  to  one-half  of  that  of  the 
pure  oxy-hydrogen  flame,  or  2827°.  The  foregoing  is  mainly  de- 
signed to  give  a  comprehensive  insight  into  the  process  of  combus- 
tion, and  the  degree  of  heat  evolved.  If  we  apply  this  simple  rule 
to  practice,  we  shall  soon  ascertain  why  some  kinds  of  fuel  pro- 
duce so  low  a  temperature,  and  why  wet  or  green  wood  does  not 
produce  the  same  degree  of  heat  as  dry  wood. 

This  calculation  is  easily  applied  to  any  fuel  with  whose  che- 
mical composition  we  are  familiar.  It  also  furnishes  us  with  a 
comparative  idea  of  the  temperatures  produced  in  certain  processes 
of  combustion.  In  the  heat  of  the  hydrogen  flame,  burning  in 
atmospheric  air,  we  melt  thin  platinum  wire;  therefore,  the  melting 
heat  of  platinum  cannot  be  more  than  28.27°.  The  temperature 
required  for  melting  iron  is  far  lower  than  that  required  for  melting 
platinum ;  from  this  fact,  we  may  conclude  that  the  heat  in  a  blast 
furnace  can  never  be  higher  than  that  by  which  platinum  melts. 

XI.  Analysis  of  Fuel. 

A  perfect  chemical  analysis  of  fuel  is,  for  our  purpose,  unneces- 
sary ;  but  an  approximate  analysis  may,  in  some  cases,  be  useful, 
and  in  other  cases,  prevent  great  evils. 

If  we  know  the  amount  as  well  as  the  quality  of  the  ashes,  and 
where  necessary,  the  amount  of  bitumen,  contained  in  fuel,  we  may 
consider  ourselves  sufficiently  safe  for  some  enterprises.  To  analyze 
fuel,  let  us  find  the  amount  of  water  it  contains,  by  exposing  it  fora 
time  to  such  a  heat  as  will  not  char  nor  kindle  it.  It  should  be 
weighed  in  its  raw  state,  and  after  it  is  dried.  If,  after  weighing  a 
pound  of  green  wood,  or  raw  coal,  we  put  it  on  the  top  of  a  puddling 
furnace,  or  on  the  arch  of  a  hot  air  stove,  leave  it  there  one  or  two 
days,  and  then  again  weigh,  we  shall  perceive  a  loss  in  weight ; 
this  loss  will  indicate  the  amount  of  water  which  the  fuel  contains. 
Ashes  are  the  residue  of  the  combustion  of  fuel.  To  obtain  them, 
it  is  best  to  break  the  specimen  into  small  fragments;  to  put  these 
fragments  into  an  iron  vessel  without  a  cover ;  then  to  put  this 


138  MANUFACTURE    OF  IRON. 

vessel  over  a  fire.  In  this  way,  the  fuel  will  burn  very  slowly. 
The  contents  of  the  vessel  should  not  be  stirred,  for  the  ashes  are 
apt  to  retain  carbon,  even  though  a  high  heat,  with  abundance  of 
air,  is  applied.  Slow  combustion  and  low  temperature  are  the 
surest  means  of  avoiding  this  evil.  The  remains  of  such  a  com- 
bustion, properly  calculated,  will  give  the  per  centage  of  ashes 
contained  in  the  fuel.  The  quality  of  the  ashes  it  is  of  but  little 
consequence  to  know. 

In  many  cases,  a  rough  estimate  of  the  bitumen  contained  in 
raw  coal  is  very  useful.  This  may  be  arrived  at  by  exposing  a 
given  amount  of  the  fuel,  in  an  iron  pot,  with  a  fitting  lid,  or  in 
a  common  cast  iron  water  kettle,  to  a  red  heat.  This  may  be 
done  in  a  common  grate.  The  vessel  must  be  left  on  the  fire 
for  five  or  six  hours.  The  coke  which  remains  will  be  similar 
in  amount  to  that  derived  from  the  process  pursued  in  the  coke 
yard.  The  losses  are  fugitive  gases,  and  represent  what  is  gene- 
rally understood  by  bitumen. 

The  amount  of  sulphur  contained  in  a  given  specimen  of  fuel,  it 
is  very  difficult  to  determine.  Even  a  perfect  chemical  analysis 
would  be  of  no  practical  use ;  because  specimens  selected  with  the 
greatest  care  from  a  pile  of  coal  do  not  contain  a  uniform  amount 
of  sulphur. 


REVIVING   OF  IRON.  139 


CHAPTER   III. 

REVIVING  OF  IRON. 

IF  ores  contained  no  foreign  matter,  or  if  they  were  peroxides, 
the  reviving  of  iron  from  its  ^ores  might  easily  be  effected.  But 
such  is  not  the  case.  The  manufacture  of  iron  is  so  highly  com- 
plicated by  the  great  mass  of  impure  ores,  that  it  has  been  found 
necessary  to  divide  it  into  several  distinct  branches.  This  division 
affords  the  advantage  of  perfecting  these  branches  of  the  manufac- 
ture, and  consequently  of  cheapening  the  product. 

The  reviving  of  iron  is,  at  present,  carried  to  so  high  a  state  of 
perfection  that  scarcely  any  improvement,  in  this  department,  can 
be  conceived,  at  least  so  far  as  yield  of  iron  is  concerned.  But 
the  quality  of  the  metal,  and  economy  of  fuel,  have  not  received  a 
corresponding  degree  of  attention. 

Among  the  ancients,  bar  iron  was  made  directly  from  the  ore. 
This  method  of  making  iron,  practiced  in  some  parts  of  Asia  at 
the  present  day,  is,  of  all  others,  the  most  ancient.  By  this  method, 
the  ore  is  smelted  along  with  charcoal  in  a  temporary  smith's 
forge ;  the  bellows  are  urged  by  hand ;  and  the  iron  forged  on 
heavy  stones  or  anvils. 

Another  method,  at  present  practiced  in  many  parts  of  Europe 
and  in  this  country,  is  what  is  generally  known  as  that  of  the  Cata- 
lan forge,  which  was  in  use  among  the  ancient  Romans.  Of  these 
two  modes  of  reviving  iron,  we  shall  speak  at  greater  length  in  the 
next  chapter,  as  they  will  be  more  properly  considered  when  we 
come  to  speak  of  the  manufacture  of  bar  iron.  We  shall  confine 
our  attention,  at  present,  to  crude  metal,  pig  metal,  and  the  appa- 
ratus employed  for  its  manufacture.  Pig  metal,  or  cast  iron,  is  a 
mixture  of  different  metals,  metalloids,  carbon,  phosphorus,  sulphur, 
&c.,  and  oxides;  in  which  iron  and  carbon  are  the  preponderating 
elements.  The  amount  of  carbon  and  other  matter  varies  greatly  in 
different  kinds  of  metal,  and  the  quality  and  quantity  of  these  ad- 
mixtures constitute  the  value  of  the  metal.  Pig  metal  differs  from 
bar  iron  only  in  this  respect,  that  it  melts  at  a  lower  temperature. 


140  .       MANUFACTURE    OF  IRON. 

The  chemical  composition  of  bar  iron  differs  so  little  from  that  of 
cast  iron,  that  any  criterion  based  upon  this  difference  is  practi- 
cally valueless.  The  making  of  pig  metal  is  the  first  process  in  the 
manufacture  of  iron.  Pig  metal  varies  in  quality  according  to  the 
admixtures  of  foreign  matter  in  the  ore,  and  according  to  the  mode 
of  manufacturing  it.  Three  classes  of  pig  metal,  ranging  with  the 
color  of  its  fracture,  are  generally  distinguished.  The  first  is  of  a 
dark  gray  or  black  color ;  it  is  generally  sufficiently  soft  to  receive 
impressions  when  struck  with  a  hammer.  It  is  not  very  strong ;  is 
easily  broken  ;  and  shows,  when  fractured,  crystals  of  black  lead 
or  graphite,  which  is  crystalized  carbon ;  it  is  coarse  grained.  This 
kind  of  pig  metal  will  melt  at  a  lower  temperature  than  any  other ; 
and  deposits,  on  cooling,  graphite,  in  shining,  mica-like  leaves  or 
crystals.  It  contains  a  large  amount  of  carbon,  which  results  from 
too  much  coal  in  the  blast  furnace.  If  re-melted  in  the  air  fur- 
nace, or  in  the  cupola,  it  resolves  into  an  excellent  cast  iron,  which 
belongs  to  the  next  class.  The  second  class  is  gray  metal.  It  is 
tougher  and  stronger  than  the  first,  as  well  as  finer  in  grain.  It 
forms  a  good  foundry  metal ;  castings  from  it  are  strong  and  smooth. 
The  third  class  is  white  metal,  of  two  distinct  kinds.  One  is  the 
result  of  too  much  ore  in  the  blast  furnace,  and  too  heavy  burden  ; 
or,  if  the  product  of  the  common  charge,  the  result  of  lack  of  blast, 
bad  coal,  wet  weather,  inattention  of  the  keeper;  or  of  ores  con- 
taining manganese.  The  other  kind  is  generally  silvery  white,  suf- 
ficiently hard  to  scratch  glass  ;  short,  that  is,  easily  broken  ;  does 
not  receive  any  impressions  from  the  hammer,  of  crystaline  frac- 
ture, often  very  beautiful.  A  sudden  change  of  temperature  will 
sometimes  break  it.  When  struck,  it  emits  a  sound  like  that  of  a 
bell.  The  best  metal  for  the  forge  is  a  cast  between  number  two 
and  number  three,  called  mottled  iron.  It  is  white,  marked  with 
gray  spots  of  plumbago  or  graphite.  In  the  blast  furnace  this  iron 
may  be  made  advantageously ;  but  a  furnace  cannot  well  be  kept 
upon  such  a  quality. 

In  the  classification  just  given,  we  refer  only  to  charcoal  iron ;  but 
this  classification  may  be  applied  to  anthracite  and  coke  iron,  if  dis- 
tinguished in  a  manner  similar  to  the  above.  We  should  add  that  iron 
of  the  third  class  made  by  coke  or  anthracite  is  a  poor  article,  and, 
under  all  circumstances,  furnishes  inferior  bar  iron.  Nearly  every 
kind  of  pig  metal  alters  its  color,  if  suddenly  cooled  in  a  stream  of  cold 
water.  When  hot,  or  when  in  a  half  melted  condition,  the  gray  casts 
assume  a  whitish  color.  The  cause  of  this  behavior  we  will  investigate 
at  the  close  of  this  chapter.  This  change  of  color  is  not  the  result  of 


REVIVING   OF   IRON.  141 

a  loss  of  carbon,  for  such  iron  contains  as  much  carbon  as  the'gray 
iron  from  which  it  is  derived.  As  a  general  rule,  the  color  of  the 
metal  does  not  depend  upon  the  amount  of  carbon  it  contains,  for 
we  frequently  find  more  carbon  in  white  than  in  gray  pig  metal. 

We  shall  now  proceed  to  describe  the  various  modes  of  obtaining 
pig  metal,  or  cast  iron. 

I.  Reviving  Iron  in  a  Crucible. 

If  we  mix  finely  powdered  pure  oxide  of  iron  with  dry  charcoal 
powder,  place  the  mixture  in  a  Hessian  crucible,  and  then  expose 
this  crucible  to  the  melting  heat  of  iron  in  an  air  furnace,  we  obtain 
a  quantity  of  gray  cast  iron.  If  the  ore  contains,  besides  iron,  any 
foreign  matter,  as  silex,  clay,  magnesia,  and  lime,  substances  very 
refractory,  the  result  of  our  manipulations  is  seriously  impaired,  for 
the  revived  iron  retained  by  the  foreign  matter  cannot  follow  its 
gravitating  tendency.  If  the  foreign  matter  is  clay  or  silex,  the  ore 
is  partly  reduced,  forms  protoxide,  and  combines  with  the  clay  and 
silex,  from  which  it  can  scarcely  be  separated.  To  prevent  this 
combination,  we  must  have  recourse  to  stronger  alkalies  than  the 
protoxide  of  iron,  such  as  lime,  magnesia,  potash,  and  soda,  which, 
combining  with  the  clay  and  silex,  liberate  the  iron.  These  are 
the  simple  elements  of  the  theory  of  the  blast  furnace. 

II.  Stuck,  or  Wulfs  Oven — Salamander  Furnace. 
This  kind  of  furnace  is  at  present  very  little  in  use.  A  few  are  still 
in  operation  in  Hungary  and  Spain.  At  one  time  they  were  very 
common  in  Europe.  The  iron  produced  in  the  stiick  oven  has  always 
been  of  a  superior  kind,  favorable  for  the  manufacture  of  steel;  but 
the  manipulation  which  this  oven  requires  is  so  expensive,  that  it  has 
been  superseded  by  the  furnace  next  described.  Fig.  41  shows  a 
cross  section  of  a  stuck  oven ;  its  inside  has  the  form  of  a  double 
crucible.  This  furnace  is  generally  from  ten  to  sixteen  feet  high; 
twenty-four  inches  wide  at  the  bottom  and  top ;  and  measures,  at 
its  widest  part,  about  five  feet.  There  are  generally  two  tuyeres, 
a,  a ;  at  least  two  bellows  and  nozzles,  both  on  the  same  side.  The 
breast  b  is  open ;  but,  during  the  smelting  operation,  it  is  shut  by 
bricks;  this  opening  is  generally  two  feet  square.  The  furnace 
must  be  heated  before  the  breast  is  closed;  after  which,  charcoal  and 
ore  are  thrown  in.  The  blast  is  then  turned  into  the  furnace.  As 
soon  as  the  ore  passes  the  tuyere,  iron  is  deposited  at  the  bottom  of 
the  hearth;  when  the  cinder  rises  to  the  tuyere,  a  portion  is  suffered 
to  escape  through  a  hole  in  the  dam  b.  The  tuyeres  are  general!^ 


142  MANUFACTURE  OF  IRON. 

kept  low,  upon  the  surface  of  the  melted  iron,  which  thus  becomes 
whitened.     As  the  iron  rises,  the  tuyeres  are  raised.     In  about 


Fig.  41. 


Wulfs  oven. 

twenty-four  hours,  one  ton  of  iron  is  deposited  at  the  bottom  of  the 
furnace.  This  may  be  ascertained  by  the  ore  put  in  the  furnace. 
If  a  quantity  of  ore  is  charged  sufficient  to  make  the  necessary 
amount  of  iron  for  one  cast,  a  few  dead  or  coal  charges  may  then 
be  thrown  in.  The  blast  is  then  stopped;  the  breast  wall  removed; 
and  the  iron,  which  is  in  a  solid  mass,  in  the  form  of  a  salamander, 
or  stuck,  wulf,  as  the  Germans  call  it,  is  lifted  loose  from  the  bottom 
by  crowbars,  taken  by  a  pair  of  strong  tongs,  which  are  fastened  on 
chains,  suspended  on  a  swing  crane,  and  then  removed  to  an  anvil, 
where  it  is  flattened  by  a  tilt  hammer  into  four  inch  thick  slabs,  cut 
into  blooms,  and  finally  stretched  into  bar  iron  by  smaller  hammers. 
Meanwhile,  the  furnace  is  charged  anew  with  ore  and  coal,  and  the 
same  process  is  renewed. 

By  this  method,  good  iron,  as  well  as  steel,  is  always  fur- 
nished. In  fact,  the  salamander  consists  of  a  mixture  of  iron  and 
steel;  of  the  latter,  skillful  workmen  may  save  a  considerable 
amount.  The  blooms  are  a  mixture  of  fibrous  iron,  steel,  and  cast 
iron.  The  latter  flows  into  the  bottom  of  the  forge  fire,  in  which 
the  blooms  are  re-heated,  and  is  then  converted  into  bar  iron  by  the 
same  method  adopted  to  convert  common  pig  iron.  If  the  steel  is 
not  sufficiently  separated,  it  is  worked  along  with  the  iron.  This 


REVIVING   OF   IRON.  143 

would  be  a  very  desirable  process,  on  account  of  the  good  quality 
of  iron  which  it  furnishes,  if  the  loss  of  ore  and  waste  of  fuel  it 
occasions  were  compensated  by  the  price  of  bar  iron.  Poor  ores, 
coke,  or  anthracite  coal,  cannot  be  employed  in  this  process. 
Charcoal  made  from  hard  wood,  and  the  rich  magnetic,  specular, 
and  sparry  ores  are  almost  exclusively  used. 

III.  Blue  Oven — Cast  Oven. 

The  furnaces  of  this  construction  are  an  approximation  towards 
the  blast  furnace  of  the,  present  time.  Fig.  42  represents  the  blue 
oven  of  the  Germans.  Its  height  is  from  twenty  to  twenty- five 


Blue  oven. 

feet.  The  form  of  the  interior  resembles  that  of  the  modern  blast 
furnace,  a  is  the  tuyere;  the  breast  b  is  closed  with  fire  brick,  or 
fire  proof  stones.  The  bottom  slopes  towards  the  breast.  This 
furnace  is  kept  in  continuous  blast  for  three,  six,  or  more  months, 
when  the  hearth  widens  so  much  that  further  work  is  not  deemed 
profitable.  When  the  furnace  is  heated  to  a  sufficient  degree,  the 
breast  is  entirely  closed,  with  the  exception  of  a  hole  at  the  bottom 
to  let  out  the  iron,  and  of  a  hole  six  or  eight  inches  above  the 
first,  through  which  the  scorice  flow  out. 

It  is  filled  to  the  top  with  coal  and  iron,  the  supply  of  which 
is  renewed  as  the  charges  sink.  The  tuyeres  are  seldom  raised 
more  than  from  ten  to  fourteen  inches  above  the  bottom  ;  should 


144 


MANUFACTURE   OF   IRON. 


Fig.  43. 


iron  and  cinder  rise  to  the  tuyeres,  the  latter  may  be  left  off.  The 
arrangement,  generally,  is  such  that  both  may  be  let  out  through 
the  tapping  hole  for  the  iron.  But  if  the  metal  is  designed  for  the 
making  of  steel,  iron  and  cinder  are  let  off  together;  in  other 
cases,  each  is  tapped  separately.  This  furnace  is  in  common  use 
on  the  Continent  of  Europe.  It  is  well  adapted  for  the  manufac- 
ture of  steel,  and  yields  an  excellent  forge  iron ;  but  it  requires 
rich  ores,  and  an  abundance  of  charcoal.  Its  management  is 
simple  ;  it  may  be  constructed  at  little  expense  ;  and  where  rich 
ores  and  cheap  charcoal  are  available,  may  be  profitably  used  in 
this  country.  The  blue  oven  is  generally  used  where  sparry  car-, 
bonates  abound ;  and  from  the  steel  metal  which  it  furnishes, 
German  or  shear  steel  is  manufactured. 

IV.    Various  Forms  of  Furnaces. 

The  present  form  of  the  blast  furnace  occupies  the  highest 
position  in  the  scale  of  improvements  successively  made  upon  the 
Catalan  forge,  of  which  we  shall  speak  in  the  next  chapter.  The 

first  improvement  was  that  of  the  sala- 
mander furnace;  the  second,  that  of  the 
blue,  or  cast  furnace.  We  shall  illustrate 
this  gradual  improvement  in  the  follow- 
ing notice  of  the  many  various  forms  of 
blast  furnaces  at  present  in  use.  It  will 
be  sufficient  to  describe  simply  the  in- 
terior of  these  furnaces,  for  their  out- 
ward forms  present  but  little  variation. 
a.  Fig.  43  represents  the  interior  of 
a  charcoal  furnace  in  common  use  in 
the  Hartz  Mountains.  This  furnace  is 
a  peculiar  one,  on  account  of  its  very 
heavy  masonry ;  the  crucible  c  is  very 
high  and  narrow ;  the  boshes  b  are  ex- 
ceedingly flat ;  the  interior  will  receive 
a  large  body  of  coal  and  ore;  the  throat 
is  often  from  four  to  five  feet  wide,  and 
sometimes  square.  Coal  and  ore  are  ex- 
pensive in  these  regions,  and  this  fur- 
nace is  constructed  as  well  for  the  pur- 
pose of  saving  fuel,  as  for  producing  a  good  quality  of  metal.  The 
ores  in  use  are  the  red,  brown,  and  yellow  varieties  of  the  sparry 


Blast  furnace,  Hartz  Mountains, 
Germany. 


REVIVING   OF   IRON. 


145 


carbonates  frequently  mixed  with  brown  hematites,  and  brown  hy- 
drates, all  of  which  are  very  refractory.  The  furnace  is  generally 
blown  with  one  tuyere,  made  of  copper.  Hot  blast,  as  far  as  we 
are  aware,  is  only  applied  to  two  furnaces  in  that  region.  This 
furnace  is  celebrated  on  account  of  the  very  fine,  strong  bar  iron, 
and  the  white  plate  iron,  from  which  steel  is  manufactured,  which 
it  produces.  It  is  managed  like  any  other  furnace  ;  the  cinders 
flow  in  consequence  of  their  small  specific  gravity,  and  by  the  pres- 
sure of  the  blast  over  the  damstone,  which  is  generally  square,  and 
lined  with  cast  iron  plates.  The  metal  is  cast,  by  means  of  cool 
moulds  made  of  cast  iron,  into  plates  ten  or  twelve  inches  wide,  two 
inches  thick,  and  from  five  to  six  feet  in  length. 

b.   Fig.  44  represents  a  blast  furnace  at  Malapane,  Silesia.    It  is 

Fig.  44. 


Blast  furnace  in  Silesia. 

twenty-seven  feet  high;  it  is  blown  with  two  tuyeres  and  hot  blast. 
The  blast  is  heated  at  the  top.  The  crucible  is  seventeen  inches 
wide  at  the  bottom,  twenty-eight  at  the  top,  and  reaches  five  feet 
eight  inches  above  the  base  of  the  furnace.  The  boshes  are  nine 
feet  in  diameter;  the  diameter  of  the  top  three  feet  eight  inches, 
10 


146 


MANUFACTURE   OF   IRON. 


The  tuyeres  are  but  fifteen  inches  above  the  bottom  stone.  In  this 
furnace,  pine  charcoal  is  burnt ;  the  ore  used  is  a  yellow  hydrate 
of  iron,  soft  and  friable,  somewhat  resembling  common  yellow  loam. 
A  very  fine  foundry  iron,  remarkable  for  its  liquidity,  running  into 
the  finest  sand  moulds,  is  the  product  of  this  furnace.  From  this 
metal  the  greater  part  of  the  fine  Berlin  castings  are  manufactured. 
This  furnace  is  remarkable  on  account  of  the  small  amount  of  coal 
it  uses. 

c.  Fig.  45  exhibits  a  German  blast  furnace  for  the  smelting  of  bog 
ores  by  charcoal.  Though  the  bog  ores  of  southern  Prussia  are 
celebrated  for  producing  very  cold-short  iron,  yet  from  this  furnace 
a  large  number  of  good  cannon  have  been  cast  for  the  use  of  govern- 
ment. The  form  of  the  inside  of  this  furnace  varies  remarkably 
from  that  of  other  furnaces.  The  height  of  the  furnace  is  thirty 
feet.  The  crucible  a  is  at  the  bottom  seventeen,  and  at  the  top 
eighteen,  inches  in  width ;  its  height  is  five  feet  six  inches.  The 
concave  boshes  measure,  at  the  widest  part,  5,  seven  feet.  The  top, 
<?,  is  three  feet  four  inches  in  diameter,  and  forms  a  cylinder  of  two 


Fig.  45. 


Fig.  46. 


Interior  of  a  blast  furnace  for 
bog  ore. 


Interior  of  a  blast  furnace  for 
spathic  ore. 


REVIVING   OF  IRON.  147 

feet  five  inches  in  length.     A  very  small  amount  of  pine  charcoal 
is  sufficient  to  supply  this  furnace. 

d.  Fig.  46  shows  the  inside  of  a  furnace  at  Eisenerz,  in  Styria 
— the  locality  of  the  iron  mountain  of  which  we  have  previously 
spoken,  where  sparry  carbonates  are  smelted.  For  want  of  wood, 
there  are  at  this  spot  but  thirteen  furnaces,  mostly  of  this  descrip- 
tion. In  fact,  all  the  furnaces  of  the  carbonate  ore  region,  that  is, 
Styria,  Carinthia,  and  Carniola,  are  constructed  on  the  same  prin- 
ciple. The  crucible  a  is  generally  from  ten  to  thirteen  feet  high  ; 
the  boshes  b  eight  feet  nine  inches  in  diameter ;  the  top  d  from  two 
feet  seven  to  tw'o  feet  nine  inches  wide.  The  height  of  the  furnace 
is  from  thirty  to  thirty-eight  feet ;  so  that  the  upper  part  of  its  in- 
terior is  from  twenty  to  twenty-four  feet  in  height.  The  blast  is 
produced  in  square  wooden  bellows,  driven  by  waterwheels,  and 
conducted  to  the  furnace  in  two  copper  tuyeres.  The  hearth  is 
frequently  built  of  limestone,  dry  marble,  or  of  Jura  lime,  for  reasons 
which  we  shall  explain  hereafter.  The  application  of  hot  blast  has 
never  succeeded.  So  greatly  does  it  injure  the  quality  of  the  metal, 
that  the  forges  cannot  work  it  without  extreme  difficulty.  These  fur- 
naces seldom  have  a  damstone  ;  the  breast  is  walled  up,  and  a  tap- 
hole  for  the  iron  left  at  the  bottom.  But  in  many  cases,  the  cin- 
ders flow  perpetually  from  a  kind  of  dam  erected  on  the  left  side 
of  the  breast.  The  iron  is  taken  out,  at  short  periods,  in  quanti- 
ties of  200  or  800  pounds,  and  commonly  run  into  chill  moulds. 
The  pigs  are  in  the  form  of  plates  of  from  five  to  six  feet  in  length, 
twelve  inches  wide,  and  from  two  to  three  inches  thick.  Such 
plate  iron  may  be  used  for  making  either  steel  or  bar  iron ;  but  if 
designed  for  bar  iron  alone,  and  if  the  very  best  bar  iron  is  desired, 
another  mode  of  casting  the  metal  is  practiced.  The  founder  digs 
a  circular  hole,  from  twenty-four  to  thirty  inches  in  diameter,  not 
far  from  the  tapping-hole,  into  which  the  iron  falls.  The  surface 
of  the  iron  is  kept  very  clean,  by  throwing  off  the  rubbish  and  cin- 
der. By  sprinkling  it  with  a  little  water  from  the  nose  of  a  small 
watering-pot,  in  a  very  short  time  the  iron  on  the  surface  crystal- 
izes,  chills,  and  a  plate  in  the  form  of  a  rosette,  from  one-half  to 
three-fourths  of  an  inch  thick,  is  lifted  off  by  means  of  an  iron 
fork,  shaped  like  a  hay  fork,  and  laid  aside.  The  freshly  opened 
surface  of  the  liquid  iron  is  treated  in  the  same  manner  as  before ; 
and  thus  the  iron  contained  in  the  basin  is  converted  into  rosettes, 
which  decrease  in  diameter  as  the  amount  of  metal  diminishes. 
These  thin  plates,  of  a  very  rough  surface,  are  excellently  adapted 


148 


MANUFACTURE    OF  IRON. 


Fig.  47. 


for  the  manufacture  of  bar  iron,  as  well  in  the  charcoal  forge  as  in 
the  puddling  furnace.  In  the  next  chapter  we  shall  make  some 
additional  remarks  on  this  subject.  This  plate  iron  is  generally 
beautifully  crystalized,  and  is  of  a  whitish  or  mottled  color,  in 
which  a  somewhat  reddish  tinge  is  sometimes  perceptible.  The 
thicker  plates  are  generally  full  of  little  cavities  of  a  round  form, 
occasioned  by  the  disengagement  of  gases  in  the  liquid  iron. 

e.  The  old  furnaces  in  Sweden  generally  had  the  form  of  two 
elliptical  crucibles — one  put  upon  the  other,  as  shown  in  the  an- 
nexed figure.  They  were  often  thirty- 
five  feet  high,  and,  in  'most  instances, 
worked  slowly;  they  consumed  but  little 
coal,  but  yielded  only  from  two  to  three 
tons  of  metal  per  week.  Still,  this  metal 
was  of  good  quality,  though  only  from  one 
hundred  to  one  hundred  and  ten  pounds  of 
charcoal  were  required  for  one  hundred 
pounds  of  iron.  The  modern  form  of  the 
Swedish  blast  furnaces  closely  resembles 
the  form  in  general  use  at  the  present  time. 
They  are  often  from  thirty-five  to  forty  feet 
in  height.  In  Russia,  the  same  principle 
of  construction  prevails.  The  furnaces  are 
generally  large,  with  weak  blast,  and 
adapted  to  economize  fuel.  The  method  of 
constructing  these  furnaces  was  borrowed 
from  Germany.  In  fact,  the  Germans 
started  the  iron  business  in  Russia  and 
Sweden,  which  may  account  for  the  great 
similarity  in  apparatus. 

Before  we  leave  this  method,  we  shall  describe  a  furnace  recently 
built  by  the  Prussian  government  on  the  banks  of  the  Rhine.  This 
furnace  is  designed  for  the  making  of  foundry  metal  from  brown 
iron  ore,  hydrated  oxide  of  iron,  of  the  transition  formation.  The 
metal  is  of  good  quality,  and  is  used  for  castings  for  machinery  and 
cannon;  from  this  metal,  also,  the  finest  specimens  of  ornamental 
and  statuary  designs  are  cast. 

/.  Fig.  48  shows  a  section  of  the  furnace,  damstone,  and  work 
arch.  The  height  of  the  furnace  is  thirty-five  feet ;  nine  feet  eight 
inches  wide  at  the  boshes  :  the  hearth  is  five  feet  high,  two  feet  six 
inches  wide  at  the  top,  and  two  feet  at  the  bottom.  The  tuyeres 


Interior  of  a  Swedish  blast 
furnace. 


REVIVING   OF   IRON. 


149 


are  eighteen  inches  from  the  base.  The  top  of  the  furnace  is  four 
feet  in  diameter.  The  boshes  measure,  from  the  upper  part  of  the 
hearth  to  its  widest  part,  four  feet  six  inches.  The  rough  masonry 
of  the  stack  is  made  of  sandstones,  strongly  secured  by  iron  bind- 
ers. The  hearth  was  formerly  made  of  sandstone  ;  but  at  present, 

Fig.  48. 


German  blast  furnace. 

I  believe,  it  is  made  of  fire  brick.  Boshes  and  lining  of  fire  brick. 
There  are  two  linings,  one  within  the  other,  between  which  is  a  lit- 
tle space,  for  the  purpose  of  giving  room  for  expansion  and  con- 
traction ;  this  space  is  filled  with  small  fragments  of  furnace  cinder. 
The  furnace  is  built  against  a  hillside,  and  the  trunnel  head  bridge 
sprung  upon  a  wall,  raised  against  the  hill.  The  blast  is  produced 
by  three  iron  cylindrical  bellows,  of  double  stroke,  which  so  far 
equalize  the  blast  as  to  make  the  application  of  a  regulator  super- 


150 


MANUFACTURE   OF  IRON. 


fluous.  These  bellows  are  driven  by  a  waterwheel.  Two,  some- 
times three,  tuyeres  conduct  the  blast  into  the  furnace,  which  works 
with  remarkable  regularity,  and  economizes  fuel  and  blast.  The 
hot  air  apparatus  is  at  the  top  ;  and  the  air  is  conducted  through 
a  system  of  half  circular  pipes.  The  casting-house  is  built  entirely 
of  iron,  in  a  noble  Gothic  style.  It  is  one  hundred  feet  long,  the 
roof  resting  upon  iron  columns  of  twenty-four  inches  in  diameter. 
These  columns  serve  as  supports  for  cranes,  by  which  heavy  cast- 
ings and  flasks  are  lifted.  In  the  centre  of  the  building,  supported 
by  two  rows  of  columns  twenty-four  feet  in  height,  runs  a  strong 
iron  carriage,  which  serves  the  purpose  of  transporting  castings 
from  the  interior  towards  the  main  door,  and  of  lifting  them  on 
wagons. 

Before  closing  this  article,  we  shall  give  the  dimensions  of  some 
American  charcoal  furnaces. 


Fig.  49. 


Fig.  50. 


Interior  of  Cold  Spring  blast 
furnace. 


Interior  of  a  Pennsylvania  char- 
coal blast  furnace. 


g.  The  furnace  at  Cold  Spring,  New  York,  is  forty  feet  in  height 
and  nine  feet  in  width  at  the  boshes.     Its  hearth  is  six  feet  six 


REVIVING   OF   IRON.  151 

inches  high;  one  foot  nine  inches  wide  at  the  bottom,  and  three 
feet  six  inches  at  the  top.  In  this  furnace,  magnetic  ores  from  the 
neighborhood,  mixed  with  a  small  portion  of  brown  hematite,  and  a 
small  quantity  of  bog  ore,  are  those  chiefly  smelted.  These  ores  are 
somewhat  expensive,  averaging  three  dollars  per  ton.  The  gray 
pig  iron  manufactured  is  of  superior  quality,  very  fusible  and  uni- 
form. Two  tons  and  a  third  of  ore,  and  120  bushels  of  charcoal, 
are  required  to  make  one  ton  of  metal.  The  wages  of  workmen 
average  about  three  dollars  per  ton  of  iron.  A  very  small  amount 
of  coal  supplies  this  furnace. 

h.  Fig.  50  represents  one  of  the  Eastern  Pennsylvania  furnaces, 
all  of  which  are  constructed  in  a  similar  manner.  The  height  of 
this  furnace  is  thirty-two  feet ;  width  of  boshes  nine  feet  six  inches ; 
hearth  five  feet  high,  two  feet  in  width  at  the  bottom,  and  two  and 
a  quarter  feet  at  the  top.  The  rich  hydrates,  pipe  ores,  fossil  ore, 
&c.,  are  generally  used.  Two  tons  and  a  half  produce,  on  an  ave- 
rage, one  ton  of  metal.  For  each  ton  180  bushels  of  charcoal  are 
required.  Wages  of  workmen  average  two  dollars  per  ton.  At 
some  places,  the  ore  is  cheap ;  while  at  others,  it  often  costs  three 
dollars  per  ton.  There  are  places  where  but  one  dollar  per  ton  is 
paid  for  ore,  and  but  four  cents  per  bushel  for  charcoal.  This  is 
the  case  at  Lebanon,  and  at  some  adjoining  counties.  The  fur- 
naces in  operation  at  the  oldest  establishments  west  of  the  Alle- 
ghany  Mountains,  such,  for  instance,  as  the  Dover  furnace  at  the 
Cumberland  River,  Tenn.,  are  almost  a  true  copy  of  those  in  use  in 
Eastern  Pennsylvania.  Both  require  the  same  amount  of  fuel,  and 
both  yield  similar  results.  But  the  farther  we  move  west,  the  greater 
is  the  amount  of  coal  we  find  used  to  produce  a  given  amount  of 
iron.  For  instance,  at  the  Alleghany  and  Ohio  furnaces,  as  far  down 
as  Hanging  Rock  and  Portsmouth,  170  or  180  bushels  of  charcoal 
are  considered  sufficient  to  make  a  ton  of  iron;  while  in  Kentucky 
and  Tennessee,  from  200  to  250  bushels  of  charcoal  are  required  to 
produce  the  same  amount. 

V.   The  Modern  Charcoal  Blast  Furnace. 

At  the  present  time,  the  blast  furnaces  are  reduced,  in  a  greater  or 
less  degree,  to  a  general  principle.  While  they  slightly  vary  accord- 
ing to  ore,  fuel,  locality,  in  all  of  them  the  hearth  is  narrow  and 
high,  the  boshes  more  or  less  steep,  and  the  trunnel  head,  or  throat, 
from  twenty  inches  to  four  feet  wide.  The  outward  form  varies 
greatly ;  and  every  owner  or  builder  follows  whatever  arrangement  is 


152 


MANUFACTURE    OF  IRON. 


most  conformable  to  his  taste.  We  shall  give  the  result  of  our  own 
experience,  and  point  out  the  material  points  on  which  the  success 
of  smelting  mainly  depends.  Fig.  51  represents  a  section  through 


Fig.  51. 


Vertical  section  of  a  blast  furnace  designed  for  charcoal. 

work  and  back  arches  of  a  charcoal  furnace.  This  furnace  has  two 
tuyeres,  and  is  designed  to  smelt  hydrates  of  the  oxides  of  iron, 
such  as  hematite,  brown  iron  stone,  pipe  ore,  and  bog  ores.  This 
form,  with  more  or  less  alterations,  will  serve  as  a  general  model. 
The  exterior  may,  in  all  cases,  be  the  same,  and  the  interior  altered 
according  to  circumstances.  The  whole  height  of  the  furnace  is 
thirty-five  feet.  The  hearth  measures  from  the  base  to  the  boshes 
five  feet  six  inches;  its  width  at  the  bottom  is  twenty-four  inches, 
and  at  the  top  thirty-six  inches.  The  tuyeres  are  twenty  inches 


REVIVING   OF  IRON. 


158 


above  the  base.  The  boshes  are  nine  feet  six  inches  in  diameter, 
and  measure  from  the  top  of  the  crucible  four  feet,  thus  giving 
about  60°  slope.  The  blast  is  conducted  through  sheet  iron  or  cast 
iron  pipes,  laid  below  the  bottom  stone,  into  the  tuyeres.  .  The  top 
is  furnished  with  a  chimney,  by  which  the  blaze  from  the  trunnel 
head  is  drawn  off.  Around  the  top  is  a  fence  of  iron  or  wood ; 
sometimes  of  stone.  Wood,  however,  is  preferable.  Fig.  52  shows 

Fig.  52. 


Section  of  a  charcoal  furnace  through  the  tuyere  arches. 

the  same  furnace  in  a  section  across  the  two  tuyere  arches  and  the 
tuyeres. 

a.  The  Building  of  a  Blast  Furnace. — A  furnace  should  be 
located  on  a  dry  spot,  free  from  springs  and  water  of  any  kind,  and 
not  exposed  to  floods  after  heavy  rains.  The  ground  should  be  then 
excavated,  until  the  bottom  is  sufficiently  solid  to  bear  the  heavy 


154 


MANUFACTURE   OF   IRON. 


Fig.  53. 


weight  of  the  stack.  The  foundation  should  be  at  least  one  foot 
larger  in  each  direction  than  the  base  of  the  furnace ;  that  is  to  say, 
if  the  furnace  is  thirty  feet  at  the  base,  the  foundation  ought  to  be 
thirty-two  feet  square.  Any  kind  of  hard,  large  stones  may  be  used 
to  fill  the  excavation.  No  mortar  should  be  used  in  the  stone  work. 
We  should  be  careful  to  leave  some  channels  through  which  rain  or 
spring  water,  in  case  it  should  penetrate  the  foundation,  may  flow 
off.  Such  a  drain  should  be  carefully  walled  up  and  covered.  The 
cavities  or  channels  for  the  blast  pipes  are  to  be  placed  level  with 
the  ground  ;  and  the  four  pillars  of  the  furnace  then  laid  out.  Fig. 

53  shows  the  arrangement  of 
the  pillars,  and  that  of  the 
channels  for  the  blast  pipes 
a,  a.  If  the  stack  is  thirty  feet 
at  the  base,  the  -work  arch  b 
may  be  fourteen  feet  wide. 
Eight  feet  are  thus  left  on  each 
side  of  the  pillars.  The  tuyere 
arches  c,  c,  c  measure  ten  feet, 
which  leaves  ten  feet  pillars. 
The  size  of  the  room  in  the 
centre  is  to  correspond  with  the 
diameter  of  the  boshes  ;  that  is, 
nine  and  a  half  feet.  This  is  to 
be  measured  from  the  centre  of 
the  stack  by  drawing  a  circle  of 
four  feet  and  three-quarters  ra- 
dius. The  inside  of  the  pillars  is  to  be  built  plumb ;  on  this  the  lining 
rests.  The  walls  towards  the  arches  should  also  be  plumb ;  but  the 
outside  should  be  beveled  according  to  the  general  tapering  of  the 
stack.  The  height  of  this  stack  is  thirty-five  feet ;  its  width  is  fifteen 
feet  seven  inches  at  the  top,  and  thirty  feet  at  the  base.,  thus  leaving 
a  slope  of  two  and  a  half  inches  to  the  foot.  The  material  of 
which  a  stack  is  built  has  but  little  influence  on  the  operation  in  the 
furnace.  Building  stones  of  any  kind,  as  granite,  graywacke,  sand- 
stone, or  even  slate,  will  answer ;  but  limestone  is  not  adapted  for 
this  purpose.  The  pillars  are  to  be  built  with  great  solidity,  with  good 
mortar,  and  may  be  raised  to  the  place  in  which  the  arches  are  set. 
The  arches  are  turned  of  brick,  which  ought  to  be  hard-burned. 
Fig.  54  represents  the  work  arch;  this  commences  seven  feet  above 
the  ground,  and  forms  just  the  half  of  a  circle.  The  arch,  from 


Ground-plan  of  the  furnace  foundation. 


REVIVING   OF   IRON. 


155 


fourteen  feet  at  its  outside,  contracts  to  five  feet  aMhe  timp.  The 
tuyere  arches  are  but  ten  feet  wide,  and  twelve  feet  high;  they  con- 
tract, towards  the  interior,  to  three  feet.  The  binder  a  majj^e 
walled  in  at  the  height  of  ten  feet,  and  of  course  crosses  the  arch. 
The  stone  work  above  the  brick  arches  should  be  arched,  that 
some  of  the  pressure  on  the  latter  may  be  relieved.  The  brick 

Fig.  54. 


Front  view  of  a  blast  furnace. 

arches  have  some  advantages  over  other  arrangements.  Stone 
arches  are  very  apt  to  crack  and  split ;  and  if,  as  often  happens, 
the  blast  works  out  at  the  timp  or  tuyeres,  the  stones  crack  and  fly 
in  such  a  manner  that  it  is  dangerous  to  go  near  the  fire.  Iron 
joists  are  very  expensive ;  besides,  by  their  expansion  and  contrac- 
tion, they  weaken  the  stack.  The  brick  arch  is  very  strong,  safe, 
and  durable.  When  the  pillars  all  around  are  seven  feet  high,  the 


156  MANUFACTURE   OF   IRON. 

arches  may  be  commenced ;  also  the  rough  in-wall,  which  must  he 
four  feet  wider  than  the  lining  at  the  widest  part  of  the  boshes,  that 
is,  thirteen  feet  and  a  half  in  diameter.  This  in- wall  is  to  be  car- 
ried to  a  height  of  five  feet,  plumb,  whence  the  contraction  com- 
mences. From  this  point  to  the  top  the  contraction  is  uniform, 
and  is  1/g  inch  to  the  foot,  thus  leaving  the  top  seven  feet  wide. 
The  stone  work  above  the  arches,  or  the  place  at  which  the  binders 
commence,  ought  to  be  very  open.  Care  should  be  taken  not  to  use 
too  much  mortar;  besides,  the  mortar  must  not  be  strong,  but  should 
consist  mostly  of  coarse  sand  and  spales,  or  fragments  of  stones. 
Channels  should  be  left,  of  such  width  that  the  binders  may,  at  any 
time  after  the  furnace  is  built,  be  pushed  through  them.  These 
channels  ought  to  be  at  least  six  inches  wide;  and  from  each 
a  branch  channel  should  lead  in  a  radial  line  towards  the  interior. 
In  this  way  they  serve  as  drains  for  the  watery  vapors  from  the 
interior  of  the  masonry. 

When  the  rough  walls  are  finished,  the  lining  or  in-wall  is  to  be 
put  in.  This  must  be  constructed  of  fire  bricks  ;  or,  where  these 
cannot  be  obtained,  or  where  they  are  too  expensive,  of  fine-grained 
white  sandstone,  which  stands  the  fire  well,  does  not  crack,  and  is 
an  excellent  material.  Where  the  former  are  used,  the  work  is  very 
simple,  for  fire  bricks  are  moulded  to  the  proper  bevel.  A  long 
board,  or  scantling,  or  a  sapling,  is  cut  of  the  proper  length,  reach- 
ing from  the  pillars  to  the  top  of  the  furnace,  that  is,  twenty-eight 
feet.  A  round  wooden  pin  is  fastened  in  each  end,  on  which 
this  pole  may  be  turned.  Upon  the  pillars,  as  well  as  upon  the  top, 
a  plank  is  fastened;  in  each  of  these  planks,  an  augur  hole  just  in 
the  centre  of  the  stack  or  lining  is  bored.  The  pole  is  set  in  the 
centre,  and  made  to  turn  round  its  axis.  To  this  pole  some  pieces 
of  board  may  be  fastened,  in  a  radial  direction,  on  which  an  up- 
right, giving  the  proper  bevel  of  the  lining,  is  fixed.  By  turning 
the  whole  round  its  axis,  the  interior  form  of  the  in-wall  is  moulded. 
The  mortar  used  in  the  lining  should  be  fire  clay,  mixed  with 
some  sand,  or,  what  is  better,  with  a  little  of  the  riddlings  from 
the  ore  yard  ;  these  riddlings  make  the  clay  very  tough,  and  pre- 
vent its  shrinking  and  crumbling.  Fire-brick  linings  are  un- 
doubtedly preferable  to  stone  linings ;  but  they  are  more  expensive. 
Where  stones  are  used,  they  should  be  cut  and  dressed,  according 
to  bevel  and  circle,  and  laid  in  courses  of  equal  thickness.  The 
mortar  to  be  used  is  the  same  as  that  just  described.  The  lining 
should  rest  upon  the  pillars  and  arches ;  and,  where  stones  are  used, 


REVIVING   OF  IRON.  157 

the  last  five  feet  at  the  top  should  be  built  of  fire  brick.  If  fire 
brick  cannot  be  obtained,  well-burnt  common  bricks,  which  do  not 
shrink,  and  which  are  not  brittle,  may  be  used.  Between  the  lining 
and  the  rough  wall,  a  space  of  eight  inches  is  left,  because  the 
width  of  the  fire  brick  or  stone  wall  seldom  exceeds  sixteen  inches. 
This  space  is  to  be  filled  either  with  fragments  of  stone,  or  broken 
furnace  cinders,  and  at  intervals  of  four  or  five  feet  maybe  covered 
with  a  layer  of  lime  mortar,  to  prevent,  in  case  a  stone  of  the 
lining  should  give  way,  the  penetration  of  the  blast. 

In  the  mean  time,  that  is,  while  the  lining  is  raised,  the  binders 
may  be  put  in  and  secured.  The  strongest  and  most  secure  bind- 
ers are  wrought  iron  bars,  three  inches  wide,  and  three-fourths  of 
an  inch  thick.  They  can  be  rolled  in  one  length,  and  should  be 
two  feet  longer  than  the  actual  length  across  the  stack  ;  each  end 
of  such  a  binder  is  to  be  bent  round  to  form  an  eye,  as  shown  in 
Fig.  55.  A  flat  bar  of  the  same  dimensions  as  the  binder  is  pushed 
through  this  eye ;  and  sufficient  room  is  left  for  a  key  or  wedge,  as 

Fig.  55.  Fig.  56. 


Eye  of  a  binder.  End  and  key  of  a  binder. 

shown  in  Fig.  56.  To  protect  this  end  of  the  bar  against  burning, 
in  the  blacksmith's  fire,  the  eye  is  formed  by  simply  bending  the 
bar  round,  and  by  riveting  it  in  two  places.  A  slight  welding  heat 
may  be  applied  to  the  joint.  There  should  be  five  binders  on  each 
side  of  the  furnace,  making  twenty  binders  in  all ;  as  well  as  eight 
bars  reaching  from  the  top  to  the  lowest  binder,  as  shown  in  Fig.  54. 
The  top  of  the  stack  should  be  covered  with  a  cast  iron  circular 
plate,  as  wide  inside  as  the  lining,  and  about  twenty-four  inches 
broad ;  this  plate  should  be  large  enough  to  cover  the  lining  and 
space,  as  well  as  a  small  part  of  the  rough  wall.  It  is  advisable  to 
cast  this  plate  in  two  halves ;  for  if  in  one  piece,  it  will  warp  and 
crack,  and  thus  disturb  the  trunnel  head  chimney  which  is  to  be 
put  upon  it.  Upon  this  plate  is  built  the  chimney  seen  in  Figs.  51 
and  52.  This  chimney  is  commonly  square,  because  this  form  is 


158  MANUFACTURE   OF   IRON. 

better  adapted  for  binding ;  the  inside  should  be  as  wide  as  the  top 
of  the  furnace,  and  its  height  from  ten  to  twelve  feet.  On  one  side, 
a  square  opening  is  left,  for  filling  the  furnace  ;  this  opening  must  be 
secured  by  an  iron  door,  which  is  shut  after  every  charge.  Many 
objections  have  been  raised  against  these  chimneys,  and  much  has 
been  said  in  their  favor.  An  objection  against  them  is,  that  a  care- 
less filler  will  throw  the  stock,  and  particularly  the  ore  and  lime- 
stone, mostly  towards  the  door ;  by  this  means  the  ore  is  brought  to 
the  back  of  the  hearth;  the  result  is  bad  work.  Another  objec- 
tion is,  that  the  fillers  are  very  apt  to  be  negligent,  because  the 
stock  is  not  easily  thrown  in,  and  because  great  attention  is  re- 
quired in  leveling  it.  These  disadvantages  are  merely  imaginary, 
and  regularity  and  order  will  overcome  them. 

The  advantages,  however,  are  of  a  highly  important  character, 
and  deserve  our  attention.  These  chimneys,  if  properly  managed, 
maintain  a  uniform  temperature  at  the  top ;  and  it  is  in  the  power 
of  the  manager  to  regulate  the  warmth  of  the  top,  by  simply  attend- 
ing to  the  opening  or  shutting  of  the  door.  To  be  able  to  lower  or 
raise  the  temperature  is  very  convenient,  because  some  ores  bear 
a  high  heat  at  the  top,  while  to  others  a  high  heat  is  injurious. 
Another  advantage  is,  that,  in  any  kind  of  weather,  the  flame  is 
not  troublesome  to  the  filler.  These  chimneys  are  built  and 
secured  by  binders  similar  to  those  used  in  the  stacks  of  puddling 
furnaces,  which  will  be  shown  hereafter. 

The  construction  of  the  hearth  is  a  business  in  which  the  founder 
himself  takes  an  active  part.  Still,  as  this  is  governed  by  general 
rules,  we  shall  give  a  statement,  sufficient  to  serve  our  present 
purpose,  of  the  principles  by  which  we  should  be  guided.  It  is  a 
mistaken  notion  that  every  sandstone  which  resists  fire  will  make 
good  hearthstone.  It  is  not  the  heat  which  destroys  the  hearth, 
but  the  chemical  action  of  the  materials  in  the  furnace.  The  dura- 
bility of  a  hearth  is  determined  by  the  manipulation  of  the  founder 
and  keeper.  Any  refractory  material  constitutes  hearthstone,  par- 
ticularly silex,  clay,  and  lime;  but  a  mixture  of  these  three  sub- 
stances must  not  be  applied.  The  form  of  aggregation  has  con- 
siderable influence  ;  but  of  this  we  shall  speak  hereafter.  Sand- 
stones are  mostly  used  in  this  country,  while  in  other  countries,  the 
material  varies  according  to  ore  and  fuel.  Limestone,  sandstone, 
gneiss,  granite,  plastic  clay,  or  fire  clay  is  employed,  as  circum- 
stances require.  But  sandstone  will  answer  in  all  cases,  if  the  ore 
and  fuel  are  properly  prepared.  Any  sandstone  which  is  free  from 


REVIVING   OF   IRON.  159 

iron,  or  from  lime,  or  from  matter  which  to  wards  silexacts  as  a  strong 
alkali,  may  be  used  for  hearthstones.  Its  refractory  quality  must  be 
proved  by  some  previous  test.  This  test  consists  in  drying  a  frag- 
ment of  the  rock  in  question  by  a  very  low  heat  on  the  top  of  a 
stove,  or  near  a  fire  grate,  for  twelve  or  twenty-four  hours;  and  then 
exposing  it  to  the  gradual  heat  of  a  blacksmith's  fire.  If  the  stone 
is  friable,  after  a  good  red  or  white  heat,  or  if  it  falls  to  pieces  by 
being  moistened  with  water,  we  may  conclude  that  the  rock  contains 
lime,  and  that  it  is  not  good  for  hearthstones.  But  if  the  fragment 
resists  the  first  heat  well,  and  if  it  is  still  hard  and  compact,  we 
may  expose  it  to  a  welding  heat  in  the  blacksmith's  fire,  urging  the 
bellows  strongly  for  half  or  three  quarters  of  an  hour.  If  the  stone 
resists  this  heat,  and  if  its  color  is  not  altered  to  brown,  we  may 
conclude  that  it  is  perfectly  safe  to  construct  a  hearth  of  it.  Some 
specimens  assume  a  reddish  hue  ;  but  we  must  not  thence  infer  that 
their  nature  is  not  refractory.  When  heated  in  the  blacksmith's  fire, 
the  fragment  becomes  glazed;  this  glazing  is  produced  by  the  fuel. 
Stone  coal  occasions  a  black,  and  charcoal  a  white  glaze :  the  for- 
mer is  the  result  of  sulphuret  of  iron  ;  the  latter  of  the  alkalies  of 
the  wood  ashes. 

Fig.  57  shows  the  method  by  which  hearthstones  are  commonly 

Fig.  57. 


Section  of  a  blast  furnace  hearth  through  the  damstone. 

prepared  and  arranged,  a  is  the  bottom  stone,  made  of  a  fine, 
close-grained  sandstone;  it  is  from  twelve  to  fifteen  inches  thick  ;  at 
least  four  feet  wide,  and  six  feet  long ;  it  reaches  underneath  at 


160  MANUFACTURE    OF   IRON. 

least  half  of  the  damstone  6.  This  bottom  stone  is  well  bedded  in 
fire  clay,  mixed  with  three-fourths  sand.  If  possible,  the  transverse 
section  of  the  stratification  ought  to  correspond  with  its  upper  and 
lower  surface  ;  that  is,  if  the  stratification,  in  its  native  position, 
is  horizontal,  it  here  ought  to  be  vertical.  This  arrangement  affords 
the  advantage  of  saving  the  bottom,  of  keeping  it  smooth,  and  of 
lessening  its  liability  to  injury  from  the  heavy  iron  ringers  of  the 
keeper.  After  the  bottom  stone  is  placed,  the  upper  part  of  which 
must  be  three-fourths  of  an  inch  lower  at  the  damstone  than  at  the 
back,  the  two  sidestones  c  are  laid,  imbedded  in  fire  clay.  These 
stones  must  be  at  least  six  feet  and  a  half  long,  reaching  from 
eighteen  inches  behind  the  crucible  to  the  middle  of  the  damstone. 
Their  form  is  commonly  square,  that  is,  a  prism  of  four  equal  sides : 
if  the  tuyeres  are  eighteen  inches  from  the  bottom,  the  stone  is 
eighteen  inches  high  and  eighteen  inches  wide ;  if  twenty  inches  from 
the  bottom,  the  stone  is  twenty  inches  on  each  side.  The  trans- 
verse section  of  the  grain  is  placed  towards  the  fire,  which  must  be 
the  case  with  all  the  hearthstones.  The  sidestones  are  sometimes 
square,  that  is,  the  inside  is  perpendicular  to  the  bottom ;  but  they 
are  oftener  beveled  according  to  the  slope  of  the  hearth.  This  lat- 
ter arrangement  is  preferable,  on  account  of  the  facilities  which  it 
affords  the  keeper.  Upon  these  stones  the  tuyere  stones  d  are  bed- 
ded ;  the  latter  suffer  much  from  heat,  and,  therefore,  ought  to  be 
of  the  best  quality.  They  should  be  from  twenty  to  twenty-four 
inches  square  :  and  even  larger  dimensions  would  be  advantageous. 
The  tuyere  holes/,  a  kind  of  tapered  arch,  are  to  be  cut  out  before 
the  stones  are  bedded.  These  stones  do  not  reach  further  than  to  the 
front  or  timpstone  #,  and  are,  therefore,  scarcely  four  feet  long.  The 
topstone  0,  of  no  particular  size,  is  generally  sufficiently  high  to 
raise  at  once  the  crucible  to  its  designed  height.  After  both  sides 
are  finished,  the  backstone  h  is  put  in,  which,  in  case  three  tuyeres 
are  used,  is  an  almost  cubical  block;  but  where  only  one  tuyere,  or 
two  opposite  each  other,  are  used,  this  backstone  is  frequently  made 
sufficiently  large  to  reach  from  the  bottom  to  the  top  of  the  crucible. 
The  timpstone  g  is  then  put  in  its  place;  this  stone  is  from  four  to 
five  feet  in  length,  so  as  to  overlap  both  side  tuyere  stones  ;  it  should 
be  of  good  quality.  The  timpstone  is  generally  raised  from  three 
to  four,  sometimes  even  six  or  seven,  inches  above  the  tuyere,  by 
putting  at  i,  on  both  sides  of  the  side  stones,  a  small  block  of  sand- 
stone, or,  what  is  better,  fire  brick.  The  raising  of  the  timpstone 
has  this  advantage.  In  cases  of  difficulty,  and  of  hard  work  in  the 


REVIVING  OF   IRON. 


161 


furnace,  the  keeper  is  enabled  to  reach  with  a  ringer  above  the 
tuyere.  Where  argillaceous  or  clay  ores  of  gray  iron  are  smelted, 
this  is  necessary.  The  opening  left  by  raising  the  timp  is  easily 
kept  tight  by  a  good  stopper;  for  this  purpose,  a  flanch,  which 
reaches  under  the  stone,  is  cast  to  the  timp-plate  Jc.  The  timpstone 
is  protected  by  the  timp-plate,  which  must  be  two  inches  thick,  im- 
bedded in  fire  clay,  and  secured  by  two  uprights  L  These  angular 
iron  plates  protect  the  stones  or  bricks  on  each  side  of  the  timp ; 
they  are  more  distinctly  shown  in  Fig.  58.  Besides  holding  the 

Fig.  58. 


Horizontal  section  of  a  furnace  hearth  through  the  tuyeres. 

timp-plate,  they  afford  the  advantage  of  keeping  the  forehearth 
clean;  for  the  hot  cinders  will  not  adhere  to  the  iron  plates,  but 
are  very  apt  to  stick  tenaciously  to  stones  or  brick.  At  this  stage 
of  our  work — during  the  whole  of  which  great  care  must  be  taken 
to  form  good  joints,  and  to  employ  good  refractory  mortar,  that 
is,  fire  clay  mixed  with  river  sand,  or,  what  is  preferable,  with 
sand  from  pounded  furnace  cinders — the  boshes  may  be  put  in. 
In  charcoal  furnaces,  if  steep,  these  are  generally  made  of  fire  brick, 
but,  if  built  at  an  angle  of  less  than  50°,  good  sand,  mixed  with  a 
little  fire  clay,  is  an  excellent  material.  In  the  latter  case,  the  mix- 
ture should  be  well  stirred  and  worked,  and  every  pains  should  be 
taken  that  the  compound  is  well  prepared  before  it  is  used.  It 
should  be  well  pounded  in,  and,  to  prevent  cracking,  should  be 
gradually  dried.  If  fire  bricks  are  used,  made  in  proper  form,  and  of 
the  largest  possible  size,  there  will  be  no  difficulty  in  putting  in  good 
boshes.  The  damstone  b  is  very  seldom  laid  in  its  place,  before  the 
furnace  is  properly  dried,  and  ready  for  the  blast.  Its  protecting 
plate  w,  the  dam-plate,  can  be  laid  at  any  time  after  the  furnace  is 
in  operation. 
11 


162  MANUFACTURE   OF  IRON. 

The  space  between  the  hearthstones  and  the  rough  wall  of  the 
furnace  stack  is  filled  and  walled  up  with  common  brick  or  stones; 
the  former  are  preferable,  because  they  are  softer,  and  have  less 
tendency  to  move  the  rough  wall,  by  the  expansion  of  the  hearth- 
stones. 

The  expense  of  building  a  stack  of  the  foregoing  size  varies  ac- 
cording to  locality,  and  to  the  facilities  we  have  at  our  command. 
The  rough  stonework  of  the  foundation  will  amount,  at  twenty-five 
cubic  feet,  to  200  perches.  This  foundation  may  be  laid  at  twenty 
cents  a  perch.  If  stones  can  be  quarried  and  hauled  to  the  spot  at 
forty  cents,  as  is  generally  the  case,  the  stonework  may  be  laid  at 
a  cost  of  one  hundred  and  twenty  dollars.  The  excavation,  esti- 
mating the  expense  of  removing  one  cubic  yard  of  earth  at  fifteen 
cents,  will  cost  twenty-four  dollars  and  seventy-five  cents.  The 
expense  of  the  rough  wall,  assuming  it  to  contain  nearly  600 
perches,  will  be  one  dollar  a  perch ;  if  stones  are  included,  one  dol- 
lar and  forty  cents.  Masons,  at  that  price,  will  make  a  smooth,  if 
not  a  hewn,  outside.  An  in-wall  of  stones  will  cost  nearly  100 
dollars;  one  of  fire  brick,  350  dollars.  The  cost  of  hearth  and 
boshes  may  be  calculated  at  150  dollars,  if  the  latter  are  of  fire 
brick;  but  if  of  sand,  at  100  dollars — provided,  of  course,  that  the 
materials  are  close  at  hand.  Binders,  timp-plate,  dam-plate,  and 
chimney  binders  at  the  top,  will  cost  850  dollars.  Therefore,  a 
stack  of  the  size  stated  may  be  assumed  to  cost,  on  an  average, 
from  1300  to  1600  dollars. 

Furnace  stacks  may  be  built  more  cheaply  with  bricks  than 
with  stones,  where  bricks  can  be  made  and  laid  at  a  reasonable 
cost.  The  rough  walls  of  such  brick  stacks  are  generally  not  so 
thick  as  those  of  stone ;  but,  even  though  they  were,  they  would 
not  be  more  expensive  than  stone,  if  a  thousand  can  be  laid  at  four 
dollars;  and  this  may  be  done  without  much  difficulty.  Furnace 
stacks  of  brick  have  been  built  at  various  places;  and  their  form 
above  the  boshes  is  generally  round :  they  are  then  called  cupola 
furnaces,  from  their  resemblance  to  the  cupola  of  the  foundry. 
The  Great  Western  Iron  Works,  in  Western  Pennsylvania,  erected, 
lately,  two  such  stacks;  but  these  are  partly  built  of  stone,  that  is, 
the  lower  or  square  part  beginning  at  the  ground,  and  terminating 
at  the  work  and  the  tuyere  arches.  This  kind  of  furnace  does  not 
bear  a  high  reputation  in  the  Old  World.  We  observed  them  in 
England  and  France,  where  the  general  complaint  against  them  is, 
that  they  work  irregularly,  and  consume  a  greater  amount  of  fuel  than 


REVIVING   OF  IRON. 


163 


square  stacks.  The  cause  of  these  evils  may  have  been  too  thin 
and  too  rough  walls,  which  can  easily  be  avoided.  But  these  fur- 
naces have  another  disadvantage,  that  is,  they  nearly  always  break 
the  strongest  binders.  In  addition  to  this,  they  require  too  many 
binders;  so  that,  on  an  average,  a  round  stack  is  not  cheaper  than 
the  square  stack.  There  may  be  instances,  some  of  which  we  shall 
produce  hereafter,  in  which  a  round  stack  is  preferable.  These  in- 
stances are  rare.  Still,  for  the  sake  of  those  who  may  be  disposed 
to  build  a  round  stack,  we  will  present  a  drawing  of  one  in  operation 
at  the  Great  Western  Works. 


Fig.  59. 


Fig.  60. 


Section  and  interior  of  a  cupola  blast  fur- 
nace. 


Front  view  of  a  cupola  blast  furnace,  at 
the  Great  Western  Works. 


Fig.  59  represents  a  vertical  cross  section,  and  Fig.  60  a  front 
view,  of  a  cupola  furnace  built  of  brick.  The  drawing  is  so  dis- 
tinct as  to  need  no  particular  description.  The  whole  stack  can  be 
built  altogether  of  brick;  or  partly  of  brick  and  partly  of  stones, 
as  is  the  case  at  the  Western  Works;  or  altogether  of  stone.  Stone, 
however,  would  be  very  expensive,  on  account  of  the  dressing  neces- 
sarily required.  Through  the  lower  or  square  part,  four  binders  are 
laid;  the  hoops,  of  wrought  iron  of  good  fibrous  quality,  of  the 
upper  or  round  part,  must  not  be  more  than  six  inches  apart,  and 
should  be  two  inches  wide,  and  three-fourths  of  an  inch  thick. 
Below  each  hoop  the  last  layer  of  bricks  projects  at  least  half  an 


164  MANUFACTURE   OF   IRON. 

inch ;  upon  this  layer  the  hoop  rests.  If  the  stack  is  built  of  stones, 
pieces  of  iron  bars  are  walled  in  to  support  the  hoops.  Between 
these  hoops  are  left  air  holes,  through  which  moisture  has  vent. 

b.  Starting  of  a  Charcoal  Furnace. — When  a  furnace  is  erected, 
and  ready  to  be  fired,  a  small  fire  may  be  put  in  the  hearth.  We 
should  always  be  cautious  to  give  the  interior  of  the  hearth  a 
lining  of  common  brick.  This  will  prevent,  in  a  great  measure, 
the  cracking  and  scaling  of  the  hearthstones.  The  fire  is  fed  from 
below.  Any  kind  of  fuel  will  serve  for  this  purpose,  because  the 
fire  is  only  designed  to  dry  the  masonry..  If  the  stack  is  new,  or 
if  it  is  one  which  has  been  for  a  long  time  unused,  it  is  necessary 
to  cover  the  throat  by  iron  plates,  and  to  leave  but  a  small  hole ; 
this  hole  may  be  so  regulated  that  we  may  burn  just  as  much 
fuel  as  we  choose.  Seven  weeks,  and  if  the  season  is  cold,  eight 
or  ten  weeks  of  constant  firing,  will  be  necessary  to  dry  a  new 
stack  so  that  it  can  be  charged  with  charcoal.  But  before  the  fur- 
nace is  charged,  the  temporary  lining  of  brick  in  the  hearth  must 
be  removed.  The  lower  part  of  the  furnace,  or  the  hearth,  is  to  be 
filled  gradually ;  and  the  fire  must  be  permitted  to  rise  in  a  blue 
flame  on  the  top  of  the  coal,  before  the  furnace  is  filled  higher  than 
the  boshes.  From  this  point  half  coal  and  half  brands  are  to  be 
used ;  the  latter  addition  causes  a  more  liberal  draft  of  air  in  the 
furnace.  If  the  furnace  is  quite  warm  before  putting  the  charcoal 
in,  and  if  we  are  confident  that  no  moisture  exists  in  the  masonry, 
ore  may  be  charged  after  the  furnace  is  half  filled  with  charcoal; 
but  if  we  doubt  that  moisture  is  wholly  expelled,  the  whole  stack 
should  be  filled  with  coal,  and  the  fire  kept  up  until  we  are  satisfied 
that  the  walls  are  perfectly  dry.  Where  everything  is  ready  for  the 
start,  repeated  grates  maybe  formed  to  facilitate  the  burning  of  coal, 
as  well  as  to  heat  the  furnace.  Grates  are  formed  by  laying  across 
the  timp  a  short  iron  bar,  as  high  up  as  the  damstone;  by  resting 
upon  this  bar  six  or  seven  other  bars,  or  ringers;  and  by  pushing 
their  points  against  the  backstone  of  the  hearth.  A  grate  thus 
formed  increases  draft  and  heat  to  a  considerable  degree,  and  very 
soon  brings  the  top  charges  down  into  the  hearth.  Where  ore  is 
charged  to  the  top,  the  descent  can  be  accelerated  by  leaving  the 
grate  most  of  the  time  in  the  hearth  ;  but  care  should  be  taken  that 
too  much  coal  does  not  remain  at  the  bottom,  for  this  will  injure 
the  bars.  In  this  way  the  ore  charges  may  be  brought  down  within 
twenty-four  or  thirty  hours.  But  if  we  are  not  to  put  the  blast  in, 


REVIVING   OF   IRON. 


165 


and  to  commence  smelting,  the  descent  of  the  ore  charges  may  be 
delayed  three,  even  four  days,  without  any  injury  to  the  following 
operations:  When  everything  is  in  order,  the  sinking  of  the  ore 
may  be  hastened.  This  will  be  indicated  by  melting  drops,  often 
drops  of  iron,  before  the  tuyeres.  When  these  are  seen,  the  dam- 
stone  is  to  be  laid,  imbedded  in  clay;  also  its  protector,  the  cinder- 
plate.  The  hearth  is  once  more  cleaned ;  the  hot  coal  then  drawn 
towards  the  dam,  and  covered  with  moist  coal  dust ;  after  which  a 
gentle  blast  may  be  let  into  the  furnace.  During  the  first  twenty- 
four  hours,  but  little  iron  is  made ;  most  of  the  ore  is  transformed 
into  slag ;  and  the  iron  which  comes  down  gets  cold  on  the  bottom 
stone,  where  it  is  retained.  At  this  early  stage,  it  would  not  be 
prudent  to  urge  the  blast  machine  too  fast,  for  great  caution  is  re- 
quired to  prevent  those  troubles  which  result  from  a  cold  furnace. 
These  troubles  are,  generally,  cold  iron  in  the  bottom,  and,  in  con- 
sequence of  that,  cold  tuyeres.  Gentle  blast,  small  burden,  and 
great  attention  alone  will  prevent  these  evils.  Where  a  furnace  has 
been  for  a  week  in  blast,  having  in  that  time  produced  from  nine 
to  ten  tons  of  metal,  and  where  the  hearth  is  clean,  that  is,  where 
it  is  perfectly  free  from  cold  iron,  or  clinkers,  the  burden  may  be  in- 
creased, and  the  blast  urged  more  strongly.  A  well-regulated  fur- 
nace will,  during  the  second  week,  make  from  sixteen  to  eighteen 
tons ;  and  the  same  amount  during  the  third  and  fourth  weeks.  A 
furnace,  just  started,  should  not  receive  so  heavy  a  burden  of  ore  as 
a  furnace  which  has  for  some  time  been  in  operation.  About  half 
the  regular  burden  should,  as  a  general  rule,  be  taken;  that  is, 
if  a  full  charge  of  ore  is  assumed  to  be  700  pounds,  the  start- 
ing charge  should  be  350  pounds.  This  amount  should  not  be 
increased  for  at  least  three  or  four  days,  or  one  week.  During 
this  time,  while  the  light  charges  last,  an  abundance  of  brands  along 
with  the  coal  may  be  used  for  the  purpose  of  keeping  a  clean,  open 
furnace. 

c.  Charges  of  a  Charcoal  Furnace. — The  coal  charges  of  a  char- 
coal furnace  should  have,  invariably,  the  same  bulk  or  weight. 
Why  this  rule  is  generally  observed,  we  shall  explain  at  another 
place.  The  amount  of  coal  for  one  charge  depends  somewhat  on 
the  dimensions  of  the  throat  of  the  furnace ;  but  fifteen  bushels  are 
considered  to  be  an  average  charge. 

The  ore  charges  vary  according  to  the  quality  of  the  ore  and  coal, 
and  according  to  blast  and  management.  The  method  by  which 
the  quantity  of  ore  is  determined  we  shall  investigate  at  the  close 


166  MANUFACTURE   OF  IRON. 

of  this  chapter.  The  coal  should  be,  if  possible,  dry,  coarse,  and 
hard,  and  the  pressure  of  the  blast  perfectly  in  the  power  of  the 
manager. 

d.  Practical  Remarks.  —  Inasmuch  as  charcoal  furnaces  are 
more  numerous  than  any  others  in  the  United  States;  and  inas- 
much as  they  exhibit  peculiarities  which  cannot  appropriately  be 
considered  under  the  general  head  of  blast  furnaces,  we  shall  take 
a  separate  survey  of  their  management. 

The  erection  of  a  charcoal  blast  furnace  in  a  new  locality  is  a 
precarious  undertaking;  and  that  losses,  in  case  of  failure,  should 
not  fall  heavily,  the  utmost  economy  should  be  observed.  Failure 
depends  not  so  much  on  the  material  used,  as  upon  other  circum- 
stances, at  times  beyond  our  control.  In  a  new  locality,  few,  if 
any,  roads  lead  to  the  site  of  the  furnace ;  or,  at  least,  they  are  sel- 
dom in  a  condition  suitable  for  our  purposes.  This  item  often  ab- 
sorbs more  means  and  time  than  one  can  well  conceive.  In  new 
localities,  the  proprietor  is  compelled  to  open  and  improve  almost 
every  foot  of  the  roads  which  lead  from  the  coalings  to  the  furnace, 
as  well  as  the  roads  which  lead  to  and  from  the  ore  banks.  The  dead 
work  in  mining  operations  should  be  well  considered  before  we 
venture  upon  the  erection  of  a  furnace,  for  this  item  may  augment 
the  expenses  of  a  new  establishment  to  a  degree  which  the  business 
is  unable  to  bear.  In  addition  to  this,  no  stack  should  be  built,  no 
improvements  of  any  nature  should  be  made,  before  the  price  of  the 
ore  at  the  furnace  is  well  settled. 

A  furnace  stack  is  not  so  important  an  object  as  it  is  frequently 
represented  to  be.  Its  interior,  to  be  sure,  must  be  carefully  con- 
structed ;  but  its  exterior  has  no  influence  whatever  on  the  quality 
and  quantity  of  the  product  manufactured.  Furnaces  of  a  very 
rude  form  are  in  operation  in  the  Western  States;  and,  though 
they  are  bound  and  kept  together  by  wooden  logs,  they  answer 
the  purpose  of  their  erection  as  efficiently  as  the  finest  stack  built 
of  hewn  stones  or  bricks.  In  Sweden  and  Russia,  where  good 
masons  are  not  generally  found,  many  furnace  stacks  are  but  a  pile 
of  stones,  rudely  put  together,  supported  by  wooden  binders.  In 
building  a  furnace  stack,  the  main  object  should  be  to  secure  a  dry 
foundation,  and  dry,  rough  walls.  If  water  can  penetrate  below  the 
bottom  stone,  and  keep  that  cool  by  evaporation,  no  advantages, 
however  favorable,  will  make  a  furnace  work  well.  The  iron  at 
the  bottom  will  not  only  chill,  but  if,  by  an  access  of  fuel,  it  is  kept 
liquid,  it  will  be  always  white,  and  of  inferior  quality.  Irregu- 


REVIVING   OF   IRON.  167 

larities  will  thus  be  occasioned  for  which  we  are  unable  to  assign 
any  reasonable  cause.  A  cold  or  wet  bottom  stone  occasions  more 
perplexity  than  any  other  imperfection  in  a  furnace  stack.  If 
rough  stones  without  any  mortar  are  used,  no  channel  for  conduct- 
ing the  moisture  from  the  interior  are  needed. 

The  construction  of  the  interior  has  great  influence  upon  the 
operations  of  the  furnace.  The  iron  furnaces  of  the  Old  World 
are  governed,  to  a  greater  degree,  by  the  nature  of  the  ore  than 
the  furnaces  of  this  country.  The  European  works  are  mostly 
based  upon  spathic  and  magnetic  ores;  hence  a  difference  in  the 
construction  of  the  furnaces  is  necessary.  Nine-tenths  of  our  ores 
are  either  hydrates,  or  oxides  of  iron,  and  therefore  a  somewhat  uni- 
form shape  of  the  interior  of  the  furnaces  is  admissible.  The  form 
of  the  interior  depends  upon  the  kind  of  ore  to  be  smelted ;  upon 
the  kind  of  charcoal  to  be  used,  whether  that  from  soft,  or  that 
from  hard  wood;  and  upon  the  kind  of  metal  we  wish  to  produce. 

The  height  of  a  furnace  stack  has  some  influence  upon  the 
quality  of  iron  obtained,  but  it  has  still  greater  influence  upon  the 
consumption  of  the  stock,  or  raw  material.  Thirty-five  or  thirty- 
six  feet  is,  according  to  our  experience,  the  most  favorable  height. 
Stacks  below  this  standard  consume  too  much  fuel;  those  which 
exceed  it  are  worked  with  trouble,  particularly  if  the  coal  and  ore 
are  small,  for  small  coal  and  ore  impair  the  draft.  If  we  wish  to 
enlarge  the  capacity  of  a  furnace,  it  is  better  to  widen  the  in-wall, 
that  is,  to  increase  the  diameter  of  the  boshes,  or  curve  the  verti- 
cal section,  in  such  a  way  as  to  give  the  desired  effect.  But,  if 
the  charcoal  is  coarse,  and  the  ore  not  mouldy,  but  in  pieces,  a 
stack  forty  feet  in  height  will  be  found  very  advantageous.  Where 
small  coal,  and  mouldy,  soft  ore  are  used,  the  stack  should  be  of 
less  height.  The  shape  of  the  in-wall  has  considerable  influence 
upon  the  quantity  and  quality  of  the  product.  Where  gray  iron 
is  desired,  a  hearth  of  at  least  five  and  a  half  or  six  feet  in  height, 
boshes  at  an  inclination  of  about  60°,  and  a  sufficiently  wide  throat, 
are  needed.  A  narrow  and  high  hearth  will  make  gray  iron  very 
readily ;  but  it  is  in  many  cases  unprofitable.  By  using  but  one 
tuyere,  a  width  of  twenty  inches  between  the  tuyere  and  the  oppo- 
site hearthstone  will  be  found  sufficient.  By  using  two  opposite 
tuyeres,  a  space  of  twenty-four  inches  between  them  may  be  con- 
sidered narrow. 

The  throat  or  trunnel  head  of  a  furnace  requires  our  closest  atten- 
tion, because  it  mainly  regulates  the  quantity  of  coal  consumed. 


168  MANUFACTURE    OF  IRON. 

Upon  this  subject,  the  managers  of  furnaces  differ  in  opinion  ;  but 
the  majority  are  in  favor  of  narrow  throats.  We  shall  have  an  op- 
portunity hereafter  to  speak  more  at  length  on  this  subject  At 
this  place,  we  merely  wish  to  draw  attention  to  it.  Experience 
unequivocally  proves  that  narrow  tops  consume  more  coal  than 
wide  tops ;  still  the  majority  of  our  iron  smelters,  particularly  in 
Pennsylvania,  and  throughout  the  whole  West,  adhere  to  the  old 
narrow  throat.  That  the  western  furnaces  are  not  conducted  so  ad- 
vantageously as  they  might  be  conducted,  is  clearly  proved  by  the 
unnecessary  amount  of  fuel  they  consume.  The  ores  throughout 
the  whole  Western  States  are  of  such  a  nature  as  to  facilitate  the 
saving  of  fuel.  Most  of  these  ores  are  very  porous,  hydrated  oxides. 
But  from  Berks  county,  Pennsylvania,  to  Hanging  Rock,  in  Ohio,  to 
say  nothing  of  Kentucky  and  Tennessee,  there  is  scarcely  a  furnace 
which  uses  less  than  from  160  to  180  bushels  of  charcoal  to  one 
ton  of  iron.  Very  few  of  them  use  a  less,  while  a  great  many  use 
a  greater,  amount.  There  must  be  a  cause  for  this  waste  of  fuel; 
for  waste  it  is,  inasmuch  as  furnaces  in  the  State  of  New  York,  and 
farther  east,  consume  but  from  120  to  130  bushels  to  one  ton,  under 
circumstances  less  favorable,  so  far  as  ore  is  concerned,  than  these 
establishments  enjoy.  It  may  be  partly  accounted  for  by  the  fact 
that  most  of  the  furnaces  are  worked  beyond  their  capacity ;  that 
is,  a  furnace  which  readily  produces  from  thirty-five  to  forty  tons 
per  week,  is  made  to  produce  fifty  or  sixty  tons.  This  large  amount 
of  iron  draws  heavily  upon  the  coal  consumed ;  nevertheless,  this 
circumstance  only  partially  accounts  for  the  quantity  of  coal  wasted. 
Without  entering  into  an  extensive  speculation  on  this  subject,  it 
will  be  evident  to  any  reflecting  mind  that  a  throat  of  nineteen  or 
twenty  inches  diameter,  working  upon  a  diameter  of  ten  feet  in  the 
boshes,  is  very  apt  to  press  the  largest  quantity  of  coal  towards  the 
lining ;  that  the  ore,  mixed  with  scarcely  any  coal,  will  descend 
into  the  hearth  in  almost  the  same  state  in  which  it  was  put  in 
the  furnace;  that  here  the  whole  reviving  process  is  to  be  per- 
formed ;  and  that  part  of  the  furnace  above  the  hearth  is,  if  not  en- 
tirely, at  least  to  a  great  extent,  useless — for  the  hot  gas,  or  blast 
from  the  hearth,  will  play  through  the  loose  coal  along  the  in-wall, 
and,  scarcely  touching  the  ore,  will  pass  up  to  the  throat,  where,  to- 
be  sure,  it  performs  some  service,  though  this  is  of  short  dura- 
tion. Such  furnaces,  with  extremely  narrow  tops,  we  frequently 
meet,  and  never  fail  to  find  them  good  customers  of  coal.  We  do 
not  wish  to  play  the  reformer  in  this  matter,  for  we  well  know  how 
difficult  it  is  to  eradicate  an  established  prejudice,  or  even  an  opin- 


REVIVING   OF  IRON.  169 

ion,  among  workmen  at  the  iron  manufacturing  establishments  ;  but 
by  widening  the  furnace  tops  gradually,  we  may,  by  approximation, 
arrive  at  the  improvement  which  appears  to  be  so  much  dreaded 
by  founders. 

No  attention  should  be  spared  to  economize  fuel ;  for  the  saving 
of  fuel  benefits  everybody — the  workmen,  the  master,  and  the  pub- 
lic. How  much  can  be  accomplished  in  this  way,  may  be  learned 
from  the  fact,  as  we  shall  hereafter  more  fully  show,  that  the  amount 
of  fuel  used  in  charcoal  furnaces,  where  other  things  are  equal, 
ranges  from  100  bushels  per  ton  of  iron  to  300  bushels  per  ton; 
and  that  reductions  in  the  use  of  fuel,  by  scientific  improvements, 
may  be  accomplished  in  spite  of  local  disadvantages.  Our  western 
furnaces,  however,  enjoy  local  advantages,  so  far  as  ore  and  coal 
are  concerned,  which  ought  to  enable  them  to  compete  against  the 
world  in  the  manufacture  of  charcoal  pig. 

A  furnace  may  be  worked  in  relation  to  considerations  of  an 
economical,  as  well  as  to  those  of  a  mercantile  nature.  When  the 
iron  market  is  dull ;  when  prices  are  low,  and  business  is  not 
hurried,  experiments  in  relation  to  economy  may  be  tried:  but 
when  the  market  is  encouraging,  and  prices  are  high,  it  would 
be  folly  to  disturb  the  progress  of  an  active  business,  with  the  ob- 
ject of  merely  saving  a  few  bushels  of  coal,  or  of  slightly  augment- 
ing the  price  of  ore.  In  the  Western  States,  business  has  been  so 
prosperous,  that  but  little  time  for  making  those  economical  im- 
provements which  we  conceive  to  be  necessary,  has  been  afforded. 

Blast,  is  a  subject  which  does  not  deserve  the  importance  which 
has  been  attached  to  it.  If  the  blast  machine  is  so  constructed  that 
it  can  furnish,  at  any  time,  without  fail,  2000  cubic  feet  of  air  of  one 
pound  pressure  per  minute,  blast  presents  no  difficulty.  In  every 
case  iron  bellows  or  cylinders  should  be  erected.  The  motive  power 
may  be  either  a  steam-engine  or  a  waterwheel.  Wood  is  trouble- 
some, requires  constant  care,  and  never  produces  that  constant 
and  regular  blast  which  is  so  essential  to  success.  Weak  blast  is 
frequently  the  cause  of  a  failure  in  business.  Where  everything 
about  a  furnace  is  imperfect,  an  imperfect  blast  machine  renders 
success  impossible ;  nor,  in  fact,  is  success  possible  with  one  that 
is  imperfect,  where  everything  else  is  right.  Therefore,  a  good 
blast  machine  is  the  first  requisite  at  a  furnace.  Fortunately, 
we  have  this  matter  perfectly  in  our  power,  and  we  do  ourselves 
serious  injury  if  we  fail  to  avail  ourselves  of  it.  In  this  instance, 
we  know  positively  what  to  do — what,  in  fact,  is  needed.  But  if3 


170  MANUFACTURE  OF   IRON. 

in  our  misdirected  zeal  to  save  expenses,  we  put  up  an  imperfect 
blast  machine,  we  shall  find  that  every  dollar  saved  will  be  coun- 
terbalanced one  hundredfold  by  losses  in  the  furnace. 

The  application  of  blast  in  the  furnace  deserves  investigation  in 
every  instance.  We  will  notice  some  leading  points ;  but  these 
are  not  presented  as  infallible  rules.  Soft  and  weak  charcoal 
cannot  bear  strong  blast,  and  a  pressure  of  from  half  a  pound  to 
five-eighths  of  a  pound  to  a  square  inch,  may  be  considered  suffi- 
cient ;  strong  blast  would  be  likely  to  choke  the  furnace  above  the 
tuyere,  by  depositing  charcoal  dust  in  the  boshes.  Strong,  coarse 
charcoal  will  bear  a  pressure  of  from  three-quarters  of  a  pound  to 
one  pound.  A  weaker  blast  is  very  apt  to  be  troublesome,  besides 
using  more  coal,  and  producing  white  metal.  Ore,  considered  as 
an  oxide  of  iron,  free  from  foreign  mattter,  has  no  relation  what- 
ever to  the  quality  of  the  blast;  but  it  is  different  with  ore  considered 
as  a  mixture  of  oxide  of  iron  and  foreign  matter.  The  kind  of 
blast  that  should  be  applied  depends  very  much  on  the  fusibility 
of  the  foreign  matter.  But  this  question  we  shall  discuss  in  another 
place.  The  form  of  the  interior  of  the  blast  furnace  is  of  consider- 
able importance.  A  high,  narrow  hearth  requires  stronger  blast 
than  a  furnace  without  a  hearth,  or  a  furnace  with  a  low  hearth  ; 
but  the  width  of  the  top,  in  proportion  to  the  diameter  of  the  boshes, 
is  of  more  importance  than  the  quality  or  pressure  of  the  blast. 
It  may  be  laid  down  as  a  rule,  that  the  larger  the  throat,  in  propor- 
tion to  the  boshes,  the  stronger  ought  to  be  the  blast ;  and  that  a 
narrow  top  and  wide  boshes,  while  they  permit  a  weaker  blast,  in- 
volve the  loss  of  much  fuel. 

The  air  introduced  by  the  blast  machine  into  the  furnace  should 
be  as  dry  as  possible.  The  main  reason  that  blast  furnaces  do  not 
work  so  well  during  summer  and  clear  warm  weather,  as  during  win" 
ter,  and  cold,  rainy  days  in  summer,  is,  that  a  large  amount  of  wa- 
tery vapors  is  mixed  with  the  atmospheric  air  in  hot  weather.  This 
water  is  very  injurious  in  a  furnace,  as  we  shall  hereafter  see.  To 
keep  the  air  dry,  the  blast  machine  should  be  erected  at  the  cold- 
est and  driest  spot  we  can  possibly  select.  We  should  take  especial 
care  that  it  is  not  exposed  to  the  hot  air  around  the  furnace,  and 
that  it  is  beyond  the  reach  of  the  steam-engine  ;  for  the  air  will  be 
more  moist  around  the  engine  and  the  heated  furnace  than  any- 
where else.  The  best  means  of  making  a  furnace  work  well  during 
summer  would  be  to  put  the  blast  machine  in  an  ice-cellar. 

Hot  blast  may  be,  under  some  circumstances,  advantageous ;  but 


REVIVING   OF   IRON.  171 

in  others,  it  is  decidedly  injurious.  It  is,  at  best,  a  questionable 
improvement;  and  it  may  be  doubted  whether  the  manufacture  of 
bar  iron  has  derived  any  benefit  from  it;  qualitatively,  it  has  not. 
Hot  blast  is  quite  a  help  to  imperfect  workmen.  It  melts  refractory 
ores,  and  delivers  good  foundry  metal  with  facility.  The  furnace 
should  be  carried  on  for  three  or  four  weeks  with  cold  blast,  that  the 
hearth  and  lining  should  be  heated  thoroughly  before  the  applica- 
tion of  hot  air. 

The  quantity  of  air  required  to  be  blown  into  a  stack  depends 
on  the  quantity  of  metal  produced  in  the  furnace.  But  there  is  a 
limit  to  the  amount  which  the  furnace  produces;  if  we  attempt  to 
exceed  that  limit,  loss,  instead  of  gain,  is  the  consequence.  A  nar- 
row top,  high  stack,  soft  coal,  and  imperfectly  roasted  ores,  require 
quantitatively  more  blast  than  where  opposite  conditions  exist;  but 
the  blast  must  be  weak.  A  wide  throat,  low  stack,  hard  coal,  and 
ores  well  roasted,  require  stronger  pressure,  but  a  less  volume  of 
blast.  The  changing  of  nozzles  and  tuyeres  is,  therefore,  a  matter 
of  considerable  importance,  and  the  effect  of  this  change  should  be 
clearly  appreciated  before  it  is  attempted. 

The  manner  in  which  stock  should  be  hoisted  and  delivered  at 
the  trunnel  head,  is  a  question  of  economy.  If  the  digging  of  a 
yard  is  very  expensive,  and  if  the  cost  of  stone  walls  and  a  trunnel 
head  bridge  cannot  well  be  borne,  coal  and  ore  may  be  hoisted  on 
an  Inclined  plane,  by  means  of  the  blast-engine,  or  by  water  or 
horse  power.  But,  under  all  circumstances,  there  should  be  a 
bridge  house,  sufficiently  large  to  receive  the  night  stock,  and,  where 
possible,  also  the  Sunday's  stock.  To  the  coal  and  ore  yard  the 
manager  should  pay  particular  attention.  The  coal,  after  being  un- 
loaded, must,  in  every  case,  be  left  twenty-four  hours  in  the  yard 
before  it  is  stacked  in  the  coal  houses,  for  it  very  often  happens  that 
coal  will  rekindle,  even  though  two  or  three  days  have  elapsed  since 
it  was  drawn  from  the  pits.  Soft  and  bad  coal  should  be  mixed 
with  the  old  stock,  and  immediately  used;  it  is  useless  to  store  soft 
coal,  for  it  will  crumble  to  dust.  Braise,  which  is  not  used  for  the 
burning  of  ore,  or  at  the  timp,  must  be  saved,  for  it  is  an  excellent 
fuel  for  the  burning  of  lime.  Iron  rakes,  for  drawing  coal,  are 
commonly  in  use  ;  but  they  are  very  destructive  to  charcoal,  and 
should  be  avoided  in  the  yard.  Wooden  rakes  are  preferable. 
Charcoal  exposed  to  the  influence  of  the  weather  during  the  summer 
season  suffers  but  little  in  quality;  but  snow  and  frost  are  very  in- 


172  MANUFACTURE   OF   IRON. 

jurious.  If  we  expect  good  work  in  the  furnace,  all  the  coal  must 
be  stored  under  roof  before  frost  sets  in. 

At  a  charcoal  furnace,  particularly  where  the  stacks  are  small, 
great  attention  is  to  be  paid  to  the  roasting,  breaking,  and  clean- 
ing of  the  ore.  Iron  is  revived  with  difficulty  from  imperfectly 
roasted  ores,  especially  if  the  stacks  are  low,  or  of  small  capacity. 
In  this  case,  the  ore  arrives  at  the  tuyere  in  an  unprepared  state. 
The  hearth  is  thus  left  to  do  most  of  the  work;  but  this  it  is  unable 
to  do;  the  consequence  is  that,  even  from  good-natured  ores,  bad, 
or  at  least  white  iron,  of  inferior  quality,  waste  of  stock,  and  fre- 
quent disturbance  in  the  regular  work,  will  be  the  result.  From  low 
stacks,  and  from  small  stacks,  we  cannot  expect  anything  like  fair 
work,  unless  the  ores  are  well  roasted.  Well  roasted  ores  are  of  a 
red  or  brown  color ;  they  adhere  like  dry  clay  to  the  tongue,  and  are 
easily  broken.  Where  ores  are  roasted  so  hard  as  to  melt  into 
a  clinker,  they  are  as  bad  as  though  they  were  not  roasted  at  all ; 
in  fact,  they  may  be  considered  worse,  for  such  ores  cannot  fail  to 
work  badly;  while  raw  ores  can  frequently  be  used  with  but  little 
injury.  The  breaking  of  ores  is  a  matter  of  great  importance:  ore 
that  is  too  coarse  is  injurious;  under  some  circumstances,  so  is 
coal  that  is  too  fine.  A  narrow  top  will  work  to  greater  advantage 
with  small,  than  with  coarse  ores;  and  a  wide  throat  requires  uni- 
form ore  of  not  too  small  a  size.  This  rule  holds  good  in  all  cases. 
Experience  has  clearly  proved  that  loose,  soft,  mouldy,  and  small 
ores  do  not  work  so  well  in  a  furnace  with  a  wide  top,  as  in  a  fur- 
nace with  a  narrow  top ;  and  the  reverse  is  the  case  with  hard, 
solid,  and  dry  ores,  such  as  the  specular,  magnetic,  and  spathic 
kind.  If  the  ores  are  brought  in  a  clean  state  to  the  yard,  and  if 
the  roasting  is  done  by  wood  and  small  charcoal,  but  little  clean- 
ing is  needed ;  but  if  brought  in  an  unclean  state,  and  if  stone 
coal  or  any  mineral  is  used  for  roasting,  they  should  be  carefully 
cleaned  from  the  adhering  dust.  In  every  instance,  a  careful  roast- 
ing of  the  ores  at  charcoal  furnaces  will  prove  advantageous  ;  this 
is  the  surest  means  of  saving  coal  and  blast,  and  of  avoiding  many 
annoyances  in  the  working  of  the  furnace.  Even  if  we  are  not 
particular  as  to  the  quality  of  the  metal ;  even  if  we  are  satisfied 
with  white  or  mottled  iron,  the  advantages  of  well  roasted  ores  are 
so  great,  economically  considered,  that  too  much  attention  cannot 
be  paid  to  this  branch  of  the  yard  operations. 

Of  fluxes,  and  the  mixing  of  different  kinds  of  ore,  we  shall 
speak  at  the  close  of  the  chapter.  But  as  this  is  a  subject  of  the 


REVIVING   OF   IRON.  173 

greatest  importance  ;  as  on  this  depend  the  well-being  and  success 
of  blast  furnace  operations,  it  will  not  be  inappropriate  in  this 
place  to  call  the  attention  of  the  furnace  manager  to  it.  The  ap- 
plication of  proper  fluxes,  or  the  mixing  of  ores  and  fluxes,  is  not 
only  the  basis  of  success,  but  by  this  branch  of  the  manager's 
duty  the  quality  and  the  price  of  the  metal  are  determined.  It  has 
been  proved  by  experience  that  the  great  difference  in  the  amount 
of  fuel  consumed,  varying  from  one  hundred  bushels  to  three  and 
even  four  hundred  bushels  of  charcoal  to  the  ton  of  iron,  chiefly 
depends  upon  the  composition  of  the  cinders  or  slag  :  besides  this, 
the  quality  of  the  metal  is  regularly  improved  by  applying  the 
proper  fluxes.  Some  previous  knowledge  of  the  elements  of  che- 
mistry is  required  to  enable  one  fully  to  understand  this  subject ; 
but  we  shall  endeavor  to  make  it  comprehensible,  without  employ- 
ing scientific  terms  or  technical  phrases. 

The  working  of  a  charcoal  furnace  is  not  difficult,  if  coal,  ore, 
blast,  and  stack  are  in  good  order.  The  first  cast,  after  starting  a 
furnace,  is  generally  taken  on  the  second  or  third  day ;  it  is  advi- 
sable not  to  tap  too  soon,  for  there  is  little  or  no  danger  in  delay. 
A  well-filled  crucible  for  the  first  cast  removes  all  the  adhering  cold 
clinkers  in  the  lower  parts  of  the  hearth ;  heats  the  hearth  thorough- 
ly ;  and  gives  a  fair  chance,  even  good  prospects,  to  the  following 
casts.  If,  however,  the  bottom  is  too  cold,  so  that  the  iron  congeals 
on  touching  it,  we  should  be  cautious  no-t  to  let  too  much  iron 
accumulate  in  the  hearth ;  but  we  should  tap  frequently,  and  make 
every  effort  to  produce  gray  iron,  by  which  alone  cold  iron,  sticking 
in  the  bottom,  will  be  removed.  If  the  hearth  is  cold,  if  the  ores 
are  too  refractory,  or  if,  through  other  circumstances,  clinkers 
or  cold  cinders  accumulate  in  the  hearth,  the  furnace  should  be 
frequently  opened,  and  these  obstructions  removed.  This  object, 
however,  should  be  effected  with  expedition ;  otherwise,  the  with- 
drawal of  the  blast  will  leave  the  hearth  too  cool.  If  cold  lumps 
of  cinder  are  allowed  to  accumulate,  they  will  by  degrees  reach 
above  the  tuyeres,  and  thus  the  furnace  operations  will  be  exposed 
to  the  greatest  danger ;  for,  if  no  coal  intervenes  between  these  cin- 
ders and  the  blast,  the  hearth  is  very  soon  cooled  to  such  a  degree 
that  the  descending  iron  and  cinder,  thus  rapidly  increasing,  would 
finally  bring  the  operation  to  an  entire  close,  and  compel  a  scraping 
of  the  materials  out  of  the  furnace.  If  strange  or  very  refractory 
ores  are  to  be  smelted,  it  is  advisable  to  lay  the  tuyeres  six  or 
seven  inches  above  the  timpstone,  that  the  keeper  maybe  enabled  to 


174  MANUFACTURE   OF   IRON. 

reach  with  ease  above  them,  and  remove  any  obstructions  which 
may  there  accumulate.  The  space  between  the  dam  and  tirnp  is 
very  easily  kept  tight  by  a  good  stopper  made  of  common  clay 
mixed  with  sand.  The  burning  out  of  a  timp  is  a  very  disagree- 
able occurrence.  To  prevent  this,  various  means  have  been  de- 
vised. We  shall  allude  to  one,  that  which  is  commonly  called  the 
water-timp.  This  is  a  cast  iron  pipe,  six  or  seven  inches  square, 
with  a  round  bore  of  from  one  and  a  half  to  two  inches  in  diameter. 
This  timp  is  laid  across  the  forehearth,  below  the  timpstone,  and 
kept  cool  by  a  constant  current  of  cold  water.  This  is  a  very  con- 
venient method  of  saving  the  timpstone,  and  of  preventing  the  stop- 
per from  being  blown  out ;  but  it  has  several  disadvantages.  It 
keeps  the  hearth  cool,  and  tends  to  diminish  burden  and  yield ;  and, 
what  is  a  still  greater  disadvantage,  it  tends  to  chill  the  cinders  of 
refractory  ores;  these  cinders,  when  cooled,  accumulate  so  fast,  that 
they  frequently  compromise  the  safety  of  the  furnace  operations. 
We  have  tried  this  experiment,  and  have  found  it  to  answer  exceed- 
ingly well  where  ores,  well  fluxed,  were  smelted ;  but  we  have 
found  it  accompanied  with  difficulty  and  danger  where — in  addition 
to  the  presence  of  a  strong  cinder — strong  iron,  inclined  to  white, 
was  manufactured.  Where  bog  ores  are  smelted,  and  where  a  wide 
hearth  is  in  use,  we  would  recommend  the  water-timp ;  but  in 
scarcely  any  other  case  will  it  afford  any  advantage. 

VI.   OoJce  Furnaces. 

But  few  blast  furnaces  work  coke  in  this  country,  and  even  these, 
so  far  as  we  know,  are  not  in  operation  at  the  present  time;  at  least, 
this  is  the  case  with  the  two  largest  establishments  of  this  kind, 
Mount  Savage  in  Maryland,  and  the  Great  Western  Iron  Works  in 
Pennsylvania.  That  coke  furnaces  cannot  prosper  on  the  eastern 
side  of  the  Alleghany  Mountains  is  not  strange,  for  against  the 
anthracite  furnaces  they  cannot  successfully  compete  ;  but  how  it 
happens  that  coke  furnaces  cannot  prosper  in  the  Western  States, 
is  more  than  we  are  able  to  comprehend.  Some  experiments  have 
been  made  in  Clarion  county,  Pa.,  and  some  in  Ohio,  with  raw  coal, 
which,  we  understand,  have  succeeded  exceedingly  well ;  but  the 
demand  for  pig  metal  is  very  limited  in  the  western  markets,  and 
hence  the  small  difference  in  the  price  offered  is  not  a  sufficient  in- 
ducement to  substitute  it  for  the  charcoal  iron  at  present  in  general 
use  for  foundry  purposes.  Such  small  experiments  will  doubtless 
be  succeeded  by  experiments  on  a  larger  scale.  The  use  of  raw 


REVIVING   OF   IRON.  175 

stone  coal  appears,  in  this  country,  to  be  more  advantageous 
than  that  of  coke,  because  good  hard  stone  coal  is  found  in  nearly 
every  place  where  ore  is  found;  this  is  particularly  the  case  in  the 
Western  States. 

As  there  is  but  little  prospect  of  an  addition  to  the  number  of 
coke  furnaces  which  now  exist,  we  shall  devote  but  a  limited  space 
to  this  subject.  The  construction  of  a  coke  furnace  does  not  mate- 
rially differ  from  that  of  a  charcoal  furnace,  except  in  its  dimen- 
sions, and  in  the  heavier  pressure  of  its  blast.  Its  height  varies 
from  forty  to  fifty  feet.  If  the  latter  height  is  exceeded,  the  fur- 
nace does  not  work  well.  Various  reports  on  English  blast  furnaces 
are  in  print,  to  which  we  refer  the  reader  who  desires  ample  infor- 
mation on  this  subject. 

We  shall  confine  ourselves  to  a  description  of  the  coke  furnaces 
of  this  country,  and  to  a  description  of  a  French  furnace,  which  is 
no  less  distinguished  by  its  convenient  structure  than  by  the  excel- 
lent work  which  it  produces.  Nearly  all  of  the  coke  furnaces  of 
the  United  States  are  of  the  same  form  and  dimensions;  and  they 
are,  we  believe,  copies  of  the  Lonaconing  furnace,  in  Maryland. 
This  was  the  first  coke  furnace,  whose  operation  was  successful, 
erected  in  this  country.  It  is  fifty  feet  high,  fifty  feet  at  the  base, 
twenty-five  feet  at  the  top,  and  measures  fifteen  feet  at  the  boshes. 
At  Mount  Savage,  and  at  the  Great  Western  Iron  Works,  the  only 
variation  from  these  dimensions  is  in  the  size  of  the  throat  and  the 
hearth.  The  Lonaconing  furnace  has  produced  good  foundry  pig 
metal;  this  has  seldom  been  the  case  at  Mount  Savage,  and  at 
the  Western  Works.  The  latter,  however,  succeeded,  after  many 
efforts,  in  making  the  furnace  produce  white  metal  for  the  use  of 
their  own  rolling  mill.  The  Western  Works  have  enjoyed  pecu- 
liar advantages ;  but  they  have  also  labored  under  peculiar  dis- 
advantages. Their  stock,  so  far  as  ore,  coal,  and  fluxes  are  con- 
cerned, is  cheaper  than  that  of  any  furnace  in  the  Union ;  but  the 
coal  at  their  disposal  is  the  outcrop  of  the  two  lowest  veins  in  the 
Pittsburgh  coal  basin.  These  veins  are  notoriously  very  sulphur- 
ous. Inasmuch  as  the  coal  of  that  region  is  scarce,  and  of  inferior 
quality,  it  is  a  riddle,  among  iron  manufacturers,  why  these  estab- 
lishments were  erected  at  the  precise  place  where  these  natural 
difficulties  can  never  be  removed.  The  works  at  Mount  Savage 
were  erected  on  an  equally  inconvenient  spot,  at  the  outcrop  or  tail 
of  the  Frostburgh  coal  basin ;  and  they  have  had  to  the  encounter 
same  difficulties.  So  far  as  stone  coal  is  concerned,  Lonaconing 


176 


MANUFACTURE    OF   IRON. 


appears  to  be  the  best  located  of  the  three  works.  The  Western 
Works  enjoy  the  advantage  of  a  very  cheap  and  good  ore,  a  true 
argillaceous  ore,  somewhat  calcareous,  which,  in  most  cases,  is  laid, 
at  the  furnace,  at  from  one  dollar  to  one  dollar  and  twenty-five 
cents  per  ton.  With  charcoal,  this  ore  produces  an  excellent  and 
strong  metal ;  and  many  expensive  experiments  were  made  with 
this  ore  before  coke  furnaces  were  brought  into  a  state  adapted 
for  regular  business.  Still,  it  appears  almost  impossible  to  run 
these  furnaces  upon  gray  iron.  A  whitish,  red-short  forge  pig  is 
the  quality  constantly  manufactured.  On  what  hypothesis  this  is 
to  be  accounted  for,  we  shall  hereafter  endeavor  to  explain. 

Fig.  61. 


Coke  furnace,  Great  Western  Iron  Works,  Pa. 

Fig.  61  exhibits  a  section  across  the  work  arch  and  the  back 
arch,  including  the  bridge-wall  of  a  great  western  furnace.     There 


REVIVING   OF   IRON.  177 

is  scarcely  any,  or  at  least  a  very  low,  and  considerably  tapered, 
hearth  in  the  furnace.  The  boshes  reach  down  almost  to  the  tuy- 
eres, and  that  part  alone  below  the  tuyere  is  plumb.  The  furnace 
is  provided  with  six  tuyeres,  and  with  hot  blast.  It  produces  from 
seventy  to  eighty  tons  of  forge  iron  per  week.  The  lower  part  of 
the  boshes,  which  in  other  furnaces  forms  the  hearth,  is  about  six 
feet  high.  This  part  is  made  of  sandstones  from  the  coal  measures; 
but  from  this  point  till  it  joins  the  in-wall,  it  is  made  of  fire  brick. 
In  other  respects,  this  furnace  does  not  materially  differ  from  other 
furnaces. 

VII.  Hyanges  Furnace. 

At  Hyanges,  Department  Moselle,  in  France,  there  are  three 
beautifully  constructed  blast  furnaces  for  coke,  which  work  admi- 
rably. Fig.  62  shows  a  section  across  timp  and  back ;  and  Fig. 

Fig.  62. 


Section  of  a  coke  furnace  at  Hyanges,  France. 


63  a  front  elevation.     The  stack  is  forty-six  feet  in  height,  and  it 
measures  sixteen  feet  at  the  boshes  :  height  of  hearth  six  feet,  and 
width  of  top  eight  feet.     The  exterior  of  the  furnace  is  round; 
12 


178 


MANUFACTURE    OF   IRON. 


the  rough  wall  rests  on  cast  iron  pillars,  and  cast  iron  framework. 
It  is  built  of  hewn  sandstone,  finely  dressed,  and  bound  by  wrought 
iron  hoops.  The  in-wall  is  made  of  fire  brick ;  the  hearth,  of  a 
cement  composed  of  roasted  and  pounded  quartz,  mixed  with  fire 
clay,  and  pounded  in  between  the  cast  iron  plates,  which  form  the 
cloak  of  the  hearth ;  the  boshes  are  formed  of  fire  brick,  made  of 
the  same  material  as  the  hearth,  and  air  dried.  The  damstone  is 
not  in  a  sloping  position,  as  usual  in  furnaces ;  but  a  vertical  dam 
of  fire  brick  is  erected,  in  the  middle  of  which  holes  for  tapping 

Fig.  63. 


Front  view  of  a  coke  furnace — Blast  furnace  at  Hyanges. 

the  iron  are  left.  The  dam-plate  is  protected  from  the  overflow- 
ing hot  cinders  by  a  projecting  rib  on  the  top.  In  these  furnaces, 
brown  hydrates,  very  much  resembling  the  fossiliferous  ores  of 
Eastern  Pennsylvania,  are  smelted.  The  metal  produced  is  very 
cold-short ;  but  it  is  wrought  into  bar  iron  of  the  finest  forms  and 
shapes.  A  large  amount  of  it  is  converted  even  into  sheet  iron 
and  tin  plates.  We  shall  have  occasion  to  refer  to  this  subject 
again.  In  the  chapter  on  puddling,  we  shall  explain  the  exact 
process  by  which  this  metal  is  converted  into  bar  iron. 


REVIVING  OF  IRON.  179 

As  we  have  previously  remarked,  there  is  but  little  prospect  of 
seeing  coke  furnaces  in  successful  operation  in  the  United  States. 
Nearly  every  State  in  the  Union  has  good  raw  coal  in  sufficient 
quantity,  as  well  as  of  proper  quality,  to  supply  its  furnaces. 
Whatever  else  is  necessary  to  be  said  on  the  subject  will  be  found 
in  our  general  review  of  furnace  manipulations. 

VIII.  Stone  Goal  Furnaces — Anthracite  Furnaces. 

If  the  use  of  coke  in  blast  furnaces  has,  from  various  causes, 
been  exceedingly  limited  in  the  United  States,  raw  coal  and  an- 
thracite have  been  employed  to  a  degree  which  the  most  sanguine 
could  scarce  have  conceived.  In  Eastern  Pennsylvania,  more  than, 
sixty  blast  furnaces,  supplied  by  anthracite,  are,  at  the  present  time, 
in  operation.  These  produce,  on  an  average,  from  severity-five  to 
eighty  tons  of  iron  per  week.  In  addition  to  this,  many  furnaces 
are  now  in  course  of  erection.  This  immense  number  of  furnaces, 
supplied  by  stone  coal  alone,  is  the  result  of  the  last  ten  years'  in- 
dustry. The  perfection  to  which  these  have  been  brought  is  a 
security  that  nothing  can  check  their  prosperity,  or  prevent  their 
extension  in  this  country. 

It  is  not  our  purpose  to  present  an  elaborate  history  of  anthra- 
cite furnaces,  or  to  show  to  what  extent  anthracite  is  employed  in 
the  manufacture  of  iron.  Those  who  wish  information  on  this  sub- 
ject may  gratify  their  curiosity  by  referring  to  Prof.  Walter  R. 
Johnson's  "Notes  on  the  Use  of  Anthracite,"  $c. 

a.  Anthracite  furnaces  resemble,  to  a  greater  or  less  degree,  coke 
and  charcoal  furnaces.  They  are  seldom  so  high  as  coke  furnaces, 
and  their  horizontal  dimensions  are  usually  greater  than  those  of  char- 
coal furnaces.  To  avoid  unnecessary  repetition,  we  shall  give  the 
dimensions  of  several  of  these  furnaces  recently  erected  in  Eastern 
Pennsylvania.  Fig.  64  represents  a  cross  section  of  an  anthracite 
furnace  at  Reading,  belonging  to  Mr.  Eckert.  Its  height  is  thirty- 
seven  and  a  half  feet ;  the  top  or  throat  six  feet  in  diameter : 
height  of  hearth  five  feet ;  tuyeres  twenty-two  inches  above  its  bot- 
tom :  the  hearth  is  five  feet  square  at  the  base,  and  six  feet  at  the 
top.  The  boshes  are  inclined  sixty-seven  and  a  half  degrees,  or  at 
the  rate  of  six  inches  to  the  foot,  and  measure  fourteen  feet  at  their 
largest  diameter.  At  the  point  where  the  slope  of  the  boshes  joins 
the  lining,  a  perpendicular,  cylindrical  space,  five  feet  in  height,  com- 
mences ;  from  the  latter  point  the  general  taper  to  the  throat  is  con- 
tinued in  a  straight  line.  The  hearth,  as  well  as  the  boshes,  is  built 


380  MANUFACTURE   OF   IRON. 

of  coarse  sandstone ;  but  the  latter  are  covered  with  a  lining  of 
fire  brick  nine  inches  thick.     The  in-wall  consists  of  two  linings; 

Fig.  64. 


Anthracite  furnace  at  Reading,  Pa. 

the  interior  is  the  lining  which  covers  the  boshes :  outside  of  this 
is  a  space  four  inches  wide,  filled  with  coarse  sand ;  and  this  is 
protected  by  a  rough  lining  of  slate,  two  feetthick.  Thorough  walls 
of  the  stack  are  not  heavy ;  but  they  are  well  secured  by  binders. 
b.  Two  furnaces,  lately  erected  at  the  Crane  Works,  near  Allen- 
town,  may  be  considered  the  latest  improvement.  (Fig.  65.)  The 
stack  is  thirty-five  feet  high ;  forty  feet  square  at  the  base,  and 
at  the  top  thirty-three  feet.  This  furnace  is,  therefore,  but  slightly 
tapered,  and  requires  heavy  stonework.  It  generates  steam  from 
the  trunnel  head  gas  flame.  At  most  anthracite  furnaces,  this  is 
done  by  putting  the  boilers  on  the  top  of  the  furnace.  The  hearth 
is  five  feet  high,  four  feet  square  at  the  bottom,  and  six  feet  at  the 
top ;  the  inclination  of  the  boshes  is  75°,  and  the  cylindrical  part 
of  the  in-wall  above  the  boshes  is  eight  feet  high,  and  twelve  feet 
in  diameter.  From  the  cylindrical  part  up  to  the  top,  which  is 
six  feet  in  width,  the  in-wall  runs  in  a  straight  line. 


REVIVING   OF  IRON. 


181 


c.  Fig.  66  represents  one  of  Messrs.  Reeves  and  Company's  fur- 
naces at  Phoenixville,  Pa.    Its  height  is  thirty-four  feet.   The  hearth 


Steam-boiler. 


Section  of  an  anthracite  furnace  at  Allentown,  Pa. 


Ffe.  66. 


is  six  feet  high,  four  feet  three  inches  square  at  the  bottom,  and  five 
feet  three  inches  at  the  top.  The  boshes 
taper  68°,  or  at  the  rate  of  rather  less 
than  six  inches  to  the  foot.  They  mea- 
sure thirteen  feet  at  their  widest  part, 
Careshouldbe  taken  that  theliningand 
the  boshes  form  a  gradual  curve,  that 
sticking  and  scaffolding  in  the  boshes 
maybe  obviated.  The  top  of  this  fur- 
nace is  eight  feet  square.  There  is -no 
doubt  that  the  form  and  construction  of 
these  anthracite  furnaces  have  been 
carried,  within  the  short  space  of  a 
few  years,  to  so  high  a  state  of  per- 
fection as  to  leave  but  little  room  for 
future  improvements.  Their  shape  is 
worthy  of  imitation,  particularly  by 
Western  manufacturers,  for  coal 
adapted  to  all  of  these  furnaces  is 
abundant  in  the  West. 


Interior  of  an  anthracite  furnace 
at  Phcenixville,  Pa. 


182  MANUFACTURE   OF  IRON. 

The  practical  working  of  these  furnaces  will  be  explained  else- 
where. We  shall  merely  remark,  in  this  place,  that  most  of 
them  generate  the  steam  for  the  motive  power  of  the  blast,  as 
well  as  the  heat  for  the  hot  blast  apparatus,  at  the  top  of  the  fur- 
nace. In  this  way,  expense  is  not  only  saved,  but  a  uniform  gene- 
ration of  steam  and  heating  of  air  are  produced.  In  relation  to 
the  building  of  coke  or  stone  coal  furnaces,  it  is  not  necessary  to 
enter  into  particulars,  inasmuch  as  the  principles  applicable  to 
these  furnaces  are  applicable  to  charcoal  furnaces.  The  cost  of 
erecting  such  a  furnace,  it  is  almost  impossible  to  state,  for  this 
will  depend  upon  locality,  material,  wages,  and  individual  tastes. 
But  it  may  be  laid  down,  as  a  general  rule,  that  a  stone  coal  fur- 
nace costs  less  than  a  coke  furnace  ;  and  that,  in  most  cases,  a 
good  charcoal  stack  can  be  altered  so  as  to  serve  for  stone  coal. 

In  the  Western  States,  many  charcoal  furnaces  are  in  operation, 
and  there  is  no  limit  to  their  extension,  so  far  as  raw  material, 
wood,  and  ore  are  concerned.  One  circumstance,  however,  will 
necessitate  the  introduction  of  stone  coal  furnaces  in  the  West; 
that  is,  the  price  of  charcoal  iron.  Some  localities  can  success- 
fully compete  against  stone  coal  iron ;  but  those  which,  besides 
enjoying  that  advantage,  are  situated  near  navigable  streams  or 
canals,  are  very  few  in  number.  We  believe  that  the  average  cost 
of  producing  charcoal  pig  at  Pittsburgh  is  twenty  dollars ;  some 
furnaces  produce  it  at  a  cost  of  fifteen  dollars.  In  as  many  cases, 
however,  twenty-five  dollars  is  paid  for  iron.  The  market  price 
at  Pittsburgh  has  varied,  for  the  last  two  years,  from  twenty-five 
to  thirty  dollars,  according  to  quality.  At  this  price,  but  little 
profit  is  left  to  the  owners  of  the  furnaces.  How  far  the  stone 
coal  furnaces  are  in  advance  of  this,  will  be  shown  by  the  follow- 
ing statement  of  the  average  result  of  three  year's  smelting.  This 
statement  has  been  furnished  by  Mr.  Reeves,  of  Philadelphia  : — 

AMOUNT   OF   MATERIAL    CONSUMED   TO  PRODUCE  ONE   TON  OF  IRON  AT    ANTHRACITE 
FURNACE  NO.  1,  AT  PHCENIXVILLE. 

Iron  ore  2.59  tons. 

Anthracite  coal       -  1.83  ton. 

Lime      -        ...  1.14    " 

AMOUNT  CONSUMED  AT  FURNACE  NO.  2,  AT  THE  SAME  PLACE. 

Iron  ore           -                                     -         2.65  tons. 
Anthracite  coal       -  1.89  ton. 

Lime 1.15    " 


REVIVING    OF  IRON.  183 

These  furnaces  smelt  brown  hematite,  hydrated  oxide  of  iron. 
If  the  Western  iron  manufacturers  apply  these  numbers  to  their 
localities,  they  will  find  that  the  manufacture  of  cheap  iron  is  per- 
fectly in  their  power.  The  wages  for  producing  one  ton  of  an- 
thracite iron,  including  incidental  expenses,  amount  to  two  dollars 
and  fifty  cents ;  to  which  is  to  be  added  the  interest  on  capital 
employed. 

IX.  The  Management  of  Blast  Furnaces. 
We  have  already  alluded  to  the  practical  management  of  blast 
furnaces;  but  in  this  place  we  shall  examine  the  subject  more  ex- 
tensively. After  the  rough  walls  of  a  furnace  are  completed,  the 
lining  and  hearth  are  to  be  put  in.  Of  the  geometrical  form  of  the 
hearth  and  in-wall  we  shall  speak  in  another  place,  and  at  present 
confine  our  attention  to  the  material  of  which  they  are  made. 

a.  The  chemical  composition  of  the  material  of  a  lining  is  of  little 
consequence  to  the  manipulations,  and  to  the  results  of  the  smelting 
process.  A  material  sufficiently  refractory  to  resist  a  moderate  heat, 
but  of  such  an  aggregate  form  as  to  permit  of  frequent  changes 
in  temperature,  is  all  that  is  needed.      Of  all  the  known  native 
and  artificial  materials,  none  answers  better  than  a  well-made  fire 
brick.     Where  fire  bricks  are  very  expensive,  or  where  they  cannot 
easily  be  procured,  a  stone  in-wall  may  be  put  in ;  but  the  applica- 
tion of  stone  is  restricted  to  charcoal  furnaces,  where  well-roasted 
ores  and  high  stacks  are  employed.     In  no  other  case  can  a  stone 
or  slate  lining  answer  the  purposes  of  a  good  in-wall ;  and  even 
where  employed  through  necessity,  difficulties  of  a  serious  nature 
may  be  apprehended,  such  as  the  falling  out  of  stones,  or  the  caving 
in  of  whole  parts.     Any  refractory  sandstone,  or,  a  still  better 
material,  silicious  slate,  will  answer  the  purpose  of  such  in-walls. 
Two  or  more  concentric  in-walls,  one  within  the  other,  have  no 
specific  use.     A  second  in-wall  will  be  serviceable  where  the  inte- 
rior lining  caves  in,  and  where  a  continuance  of  the  smelting  opera- 
tions is  desirable.     Such  a  lining,  made  of  good  slate,  like  that 
shown  in  Fig.  64,  will  answer  every  purpose. 

b.  The  hearth  is  a  very  important  part  of  a  blast  furnace.     A 
variety  of  materials  are  used  in  its  construction.     In  Sweden  and 
Russia,  granite,  gneiss,  or  porphyry:  in  Austria,  sandstone :  in  most 
of  the  furnaces  of  the  Alpine  Mountains,  marble — at  least  in  them 
the  bottom  stone  is  of  marble :  in  Germany  and  France,  limestone, 
marble,  sandstone,  fire  brick,  and  cement :  and  in  England  and  the 


184  MANUFACTURE   OF   IRON. 

United  States,  sandstone.  To  make  experiments  on  hearthstones, 
in  our  country,  would  be  injudicious,  for  there  is  an  abundance  of 
serviceable  material  throughout  the  United  States,  from  the  beauti- 
ful kaolin  of  Connecticut,  to  the  durable,  coarse  red  sandstone  of 
Arkansas ;  and  as  the  tendency  of  our  iron  furnaces  is  to  produce 
gray  iron,  as  this  ought  to  be  their  tendency,  and  as  the  ores  in 
use  are,  almost  without  exception,  oxides,  there  is  hardly  any  choice 
left  but  to  take  sandstones.  The  coal  fields  afford  almost  every 
variety  of  sandstone  ;  from  the  coarse,  conglomerate,  mill-stone 
grit,  to  the  fine-grained,  carburetted  sandstone  of  Portsmouth,  Ohio. 
Every  one  of  these  varieties  is  nearly  everywhere  accessible.  No 
general  tests  of  the  refractory  quality  of  the  material  in  question 
can  be  given.  The  practical  is  the  only  test  on  which  we  can  rely. 
Fire  bricks  have  been  tried,  and,  in  some  cases,  with  success ;  but 
it  is  doubtful  whether  fke  brick  will  answer  so  well  as  good  sand- 
stone, particularly  in  stone  coal  furnaces. 

c.  After  the  lining  and  hearth  are  finished,  fire  may  be  kindled. 
This  is  to  be  done  with  great  caution,  to  prevent  cracking,  or,  what 
is  worse,  flying  of  the  stones.  It  is  advisable  to  wash  a  new  lining 
and  hearth,  once  or  twice,  with  a  composition  of  lime,  clay,  and 
common  salt ;  this  mixture  will  dry  very  hard,  and,  under  a  low 
heat,  will  readily  melt  into  a  very  liquid  slag,  which  glazes  the 
whole  interior.  After  fire  is  kindled,  the  tuyere  holes  should  be 
closed,  and  the  top  covered  by  cast  iron  plates ;  this  will  prevent  a 
strong  draught,  and  a  change  of  cold  and  hot  air,  which  would  be 
destructive  both  to  hearth  and  lining.  It  is  also  advisable  to  cover 
the  sandstones  of  the  hearth  with  a  four-inch  lining  of  common 
brick,  to  prevent  the  direct  action  of  the  fire  upon  the  stones.  When 
the  hearth  and  lining  have  been  thus  exposed  to  fire  for  a  week 
or  ten  days,  they  will  doubtless  become  tolerably  dry ;  the  hearth 
may  then  be  filled  with  coal  as  high  as  the  widest  part  of  the 
boshes,  and  its  temperature  raised.  But  we  should  be  cautious  to 
keep  the  tuyeres  shut,  and  to  protect  the  timpstone  either  with  a 
stopper  of  clay  or  a  lining  of  brick.  In  filling  coal  we  should 
proceed  slowly ;  and  no  fresh  coal  should  be  applied  until  the  flame 
rises  through  the  last  charge.  The  furnace  may  thus  be  heated 
within  three  or  four  days,  if  we  are  careful  to  keep  the  coal  up,  and 
to  clean  repeatedly  below.  But  if  time  is  not  precious,  the  fore- 
hearth  may  be  closed  up,  with  the  exception  of  a  few  small  open- 
ings, with  a  brick  stopper.  This  is  to  be  taken  out  at  least  every 
twenty-four  hours,  and  the  hearth  cleaned  of  ashes  and  clinkers. 


REVIVING   OF  IRON.  185 

d.  When  a  furnace  is  well  dried  and  heated  throughout,  and 
•when  it  is  filled  to  the  widest  part  of  the  boshes,  ore  may  be  directly 
charged,  and  then  alternately  coal  and  ore,  until  the  furnace  is 
filled  to  the  brim.     In  this  state  it  must  be  constantly  kept,  how- 
ever fast  or  slowly  the  charges  may  sink.    But,  if  the  furnace  is  not 
quite  dry ;  if  we  have  any  doubt  about  the  matter;  or  if  the  stack 
is  new,  it  is  advisable  to  fill  the  whole  furnace  with  coal.     This  is 
particularly  applicable  to  charcoal  furnaces  or  small  stacks. 

e.  The  charges  of  ore  should  be  small  for  the  first  two  or  three 
days,  that  the  working  of  the  furnace  may  be  observed.     If  every 
thing  works  well ;  if  the  hearth  is  clean,  and  the  iron  gray,  the 
amount  of  ore  may  be  gradually  increased.     Limestone,  or  any 
other  material  employed  as  a  flux,  generally  equals  in  amount  a 
full  charge  of  ore,  the  object  of  which  is  to  clean  the  lining  and 
hearth  from  adherent    cold  cinder  and   clinkers.     When  coal  is 
so  far  consumed  that  the  ore  has  descended  to  the  tuyere,  the 
hearth  may  be  cleaned  once  more,  the  damstone  put  in  its  place, 
and  the  tuyeres  and  blast  prepared  for  operation.     Charcoal  fur- 
naces require  very  little  attention  at  this  time ;  but  coke  and  stone 
coal  furnaces  are  managed  with  considerable  difficulty.     Coke  and 
stone  coal  should  be  kept  almost  constantly  in  motion,  to  prevent 
the  adhesion  of  clinkers,  and  the  result  of  that  adhesion,  scaffold- 
ing.    This  may  be  done  by  putting  in  grates,  at  least  three  times 
every  day,  by  means  of  ringers  and  hand  bars,  as  we  have  hereto- 
fore explained.    Stone  coal  is  very  apt  to  prevent  the  free  passage 
of  draft,  by  depositing  small  coal,  or  dust.    Bituminous  coal,  which 
is  very  apt  to  swell,  sometimes  bakes  into  large  masses  or  cakes, 
through  which  no  air  can  pass. 

/.  The  hearth  in  small  furnaces  is  four  inches,  and  in  larger 
furnaces  eight  inches  wider  than  the  damstone.  An  opening  for  a 
tap-hole  is  thus  left.  This  hole  is  filled  up  with  a  mixture  of  re- 
fractory clay  and  sand,  mixed  with  a  little  coke  dust,  to  prevent 
its  vitrification.  The  damstone  itself  is  bedded  in  fire  clay,  and 
well  protected  by  the  dam-plate,  of  cast  iron,  two  inches  thick. 

g.  The  tuyeres  at  the  charcoal  furnaces  with  cold  blast  are 
mostly  made  from  a  refractory  fire  clay.  This  is  a  bad  habit.  The 
Swedish  and  German  method  of  employing  copper  tuyeres  is  pre- 
ferable, for  it  is  not  only  the  cheaper,  but  it  saves  a  great  deal  of 
trouble.  A  copper  tuyere  is  simply  a  piece  of  red  copper,  three- 
eighths  or  one-half  of  an  inch  thick,  bent  and  hammered  into  the 
proper  shape.  A  stone  coal  furnace  with  hot  blast  requires  a  water 


186  MANUFACTURE   OF   IRON. 

tuyere.  This  is  an  article  of  trade,  which  we  shall  describe  in 
another  place. 

h.  The  starting  of  the  blast  requires  careful  attention.  When 
the  hearth  is  clean,  the  damstone  in,  the  tuyeres  properly  placed, 
and  the  blast  machine  in  motion,  the  nozzles  of  the  pipes  are  turned 
into  the  tuyere,  and,  for  the  first  few  days,  about  half  of  the  usual 
pressure  applied.  At  the  expiration  of  one  week,  the  full  blast 
may  be  put  on,  and  the  ore  charges  gradually  increased ;  so  that  a 
furnace,  within  three  weeks — if  a  new  furnace,  within  four  weeks — 
is  able  to  produce  its  full  amount  of  iron.  It  is  advisable  to  keep 
the  hearth  for  the  first  discharges  as  full  of  iron  as  possible.  This 
is  the  best  means  of  cleaning  a  hearth  below  the  tuyere. 

I.-  What  should  be  the  height  of  the  damstone  and  cinder-plate, 
particularly  at  charcoal  furnaces,  is  a  delicate  question,  the  solution 
of  which  depends  greatly  on  ore,  flux,  blast,  and  upon  the  quality 
of  iron  to  be  produced.  The  height  varies  from  one  inch  to  three 
and  even  four  inches  below  the  tuyere.  Strong  cinder  and  gray 
iron  require  a  lower  dam  than  very  liquid  cinder  and  white  or  forge 
iron.  A  low  dam  consumes  more  fuel,  and  inclines  to  gray  iron. 
In  stone  coal  or  coke  furnaces,  we  encounter  no  difficulty  in  relation 
to  this  point,  for  the  pressure  of  the  blast  in  these  furnaces  often 
renders  it  necessary  to  raise  the  dam  several  inches  above  the  tuyere. 

Jc.  With  charcoal  a  furnace  is  worked  with  little  difficulty ;  but 
•with  coal,  and  still  more  with  coke,  the  difficulty  is  augmented.  By 
the  use  of  charcoal,  the  slag  is  generally  glassy,  liquid,  and  not  soon 
cooled  off,  if  the  blast  touches  it ;  but  the  slag  of  the  coal  or  anthracite 
furnace  is  generally  stony,  opake,  and  easily  chilled  by  the  touch 
of  the  cold  blast.  The  use  of  coke  is  accompanied  by  still  worse 
results.  Where  everything  is  in  good  order ;  where  the  fluxes  are 
•well  selected ;  where  the  ore  and  coal  are  in  proper  condition,  and 
the  blast  steady  and  dry,  scarcely  any  disturbances  happen  ;  and  a 
drawing  of  the  cinders,  with  cleaning  of  the  hearth  of  the  charcoal 
furnace  every  twelve  hours,  and  that  of  the  coal  or  coke  furnace 
every  six  hours,  is  sufficient.  However,  should  anything  go  wrong, 
and  should  the  slag  be  very  much  inclined  to  chill  before  the  blast, 
thus  obstructing  the  passage  of  the  materials,  cleaning  is  more  fre- 
quently required,  often  at  intervals  of  two  hours ;  but  this  should 
be  done  quickly,  for  in  such  cases  the  furnace  is  generally  in  a  con- 
dition in  which  it  can  dispense  with  the  blast  only  for  a  short  time ; 
and  frequent  opening  of  the  forehearth,  stopping  off  the  blast,  by 
cooling  the  hearth,  would  make  the  matter  worse.  One  of  the  great- 


REVIVING   OF  IRON.  187 

est  hindrances  of  good  work  is  the  accumulation  of  small  coal  or 
dust  in  the  boshes,  or  in  the  corners  of  the  hearth.  This  accumu- 
lation results  from  a  cold  hearth,  or  from  a  too  strong  blast.  Where 
such  accidents  happen,  aur  only  resource  is  to  raise  the  temperature 
of  the  hearth,  to  keep  the  forehearth  shut,  or,  by  means  of  cinder 
noses  on  the  tuyere,  to  throw  the  blast,  as  much  as  possible,  in  the 
centre  of  the  hearth.  If  a  hearth  is  too  cold,  and,  to  all  appearances, 
cannot  be  heated  to  its  proper  degree  by  the  utmost  care  and  atten- 
tion, it  is  advisable  to  throw  on  some  dead  charges,  that  is,  charges 
without  any  ore,  the  number  of  which  can  be  increased,  according 
to  circumstances,  to  six  or  twelve,  or  even  more.  In  some  places, 
managers  are  accustomed  to  reduce  the  ore  charges  in  cases  of  dif- 
ficulty. This  is  a  bad  habit,  where  the  obstruction  in  the  hearth  is 
but  an  accident,  and  not  the  result  of  overburdening.  If  a  fur- 
nace has  an  ore  charge,  with  which  it  has  always  worked  regularly, 
it  is  advisable  not  to  change  burden,  simply  because  a  disturbance 
happens ;  but  if  the  furnace  is  overburdened  by  ore,  and  in  con- 
sequence of  that  has  become  too  cold,  a  reduction  of  the  ore 
charges,  and  the  application  of  dead  charges,  in  the  mean  time, 
may  be  required. 

The  forehearth  should  be  kept  closed  up,  so  as  to  prevent  the 
blowing  out  of  the  flame.  There  is  no  use  whatever  in  blowing 
out  below  the  timp ;  the  heat  and  blast  lost  there  are  quite  ser- 
viceable in  the  stack,  and  of  no  use  whatever  at  the  timp.  They 
are,  besides,  very  apt  to  burn  the  timpstone  and  timp-plate,  and  to 
cause  a  premature  destruction  of  the  hearth.  By  keeping  the  cinder 
passage  open  across  the  timp — or,  if  sufficient  cinder  is  not  dis- 
charged for  that  purpose,  by  changing  frequently  the  cinder  pas- 
sage— a  warm  timp  may  be  kept  without  the  flame  of  the  blast. 

I.  The  keeping  of  a  furnace  has  great  influence  upon  the  success 
of  the  whole  operation.  If  a  manager  expects  workmen  to  do  their 
duty,  he  should  be  careful  to  furnish  them  with  good  tools.  Bad  or 
imperfect  tools  augment  the  difficulty  of  keeping  a  furnace ;  and 
where  disturbances  happen,  they  give  rise  to  much  trouble  and 
vexation.  Ringers,  crow  or  hand  bars,  tapping  bars,  cinder  hooks, 
shovels,  sledges,  &c.,  ought  not  only  to  be  in  good  condition,  but 
in  sufficient  number.  It  may  be  of  service,  in  instances  where  a 
manager  has  none  but  inexperienced  workmen,  to  know  the  duties 
of  the  keeper.  We  shall,  therefore,  give  a  brief  description  of  the 
furnace  operations  at  the  hearth. 

m.  The  tuyere  should  be  bright  and  star-like — a  condition  easily 


188  MANUFACTURE  OF  IRON. 

produced  by  hot  blast,  but  not  by  cold  blast  and  refractory  ores. 
Clay  and  argillaceous  ores  are  very  apt  to  chill  at  the  tuyere,  and 
form  around  it  a  body  of  cold  cinder,  which  often  increases  rapidly, 
and  disturbs  the  regular  work.  Such  cold  masses  of  cinder  are  to 
be  pushed  into  the  hearth,  and  hot  coal  left  between  them  and  the 
tuyere.  With  hot  blast  we  experience  less  difficulty ;  still,  such  ores 
require  more  attention  than  others.  In  many  cases,  where  gray 
iron  is  to  be  produced  by  cold  blast,  from  argillaceous  ores,  it  is 
necessary  to  produce  a  prolongation  of  the  tuyere,  called  a  nose, 
by  the  workmen,  by  means  of  cinder;  this  nose  is  often  extended 
far  into  the  hearth,  and  then  called  the  dark  or  black  tuyere.  In 
this  case,  a  thin  scale  of  cold  cinder,  with  numerous  holes,  forms 
around  the  tuyere;  this  scale  should  never  be  permitted  to  grow  so 
strong  that  a  slight  tap  with  an  iron  bar  is  not  sufficient  to  remove  it. 
Every  six  hours  at  coal  or  coke  furnaces,  and  every  twelve  hours  at 
charcoal  furnaces,  this  nose  is  to  be  removed ;  and  its  place  sup- 
plied by  a  new  one  as  soon  as  the  blast  is  in  operation.  If  the 
cinders  are  not  of  a  given  composition,  there  is  some  difficulty  in 
forming  such  a  prolongation  of  the  tuyere;  but  some  keepers  are  so 
skillful  as  always  to  succeed,  while  others  frequently  fail.  This  is 
a  very  advantageous  method  of  working  clay  ores ;  and  I  have  known 
instances  in  which  the  economical  advantages  of  the  hot  blast  were 
obtained  by  this  kind  of  tuyere  alone.  But,  if  the  extension  arid 
thickness  of  such  a  nose  exceed  a  certain  degree,  as  is  frequently  the 
case  where  two  or  three  tuyeres  are  at  work,  and  where  the  work- 
men are  inexperienced  and  negligent,  the  consequences  are  so 
serious  and  so  troublesome  as  to  afford  no  encouragement  to  con- 
tinue such  a  mode  of  working. 

n.  After  tapping,  or,  what  -is  the  same  thing,  after  a  new  start, 
the  hot  coals  of  the  interior  are  drawn  forward,  as  high  as  the  dam ; 
and  a  stopper,  formed  of  a  mixture  of  sand  and  clay,  is  rammed  in 
between  the  timpstone  and  the  coal,  and  so  well  secured  that  the 
blast  cannot  move  it,  and  so  tight  that  the  blast  cannot  play  between 
it  and  the  timp.  Difficulties  often  arise  in  the  latter  part  of  the 
performance.  To  avoid  these,  various  methods  have  been  employed, 
of  which  the  most  common  is,  an  iron  rib,  two  or  three  inches 
thick,  cast  to  the  timp-plate,  and  projecting  under  the  timpstone. 
Another  method,  previously  mentioned,  is  what  is  called  a  water 
timp;  but  this  improvement  is  of  a  very  doubtful  nature.  I  never 
saw  a  well-made  stopper  fail,  if  properly  attended  to :  but  if  the  clay 
is  too  soft,  and  not  sufficiently  refractory  ;  if  the  stopper  is  so  small 


REVIVING   OF   IRON.  189 

that  the  blast  can  work  through  it  and  the  timp,  of  course  no  stop- 
per will  answer.  When  the  hearth  is  well  closed,  coal  dust  or  coke 
dust  is  thrown  over  the  hot  coal,  and  after  this,  the  blast  is  turned 
into  the  furnace.  The  coal  and  dust  in  the  forehearth  must  be  suf- 
ficiently porous  to  permit  the  passage  of  the  blast,  and  to  show  a 
slight,  gentle,  blue  flame.  Within  an  hour  or  two  hours,  according 
to  the  dimensions  of  the  hearth  and  the  burden  of  the  ore,  the  cin- 
der in  the  interior  will  rise  sufficiently  high  to  stop  the  playing  of  the 
blast  through  the  forehearth ;  when  it  may  be  advisable  to  open  the 
coal,  and  to  endeavor,  by  means  of  a  short  handbar,  to  ascertain  whe- 
ther the  cinder  has  penetrated  into  the  forehearth.  If  it  has  not,  some 
stirring  and  lifting  of  the  coal  cinder,  at  the  bottom,  will  generally 
be  sufficient  to  fill  the  forehearth  with  liquid  slag.  If  a  furnace  has 
been  for  some  days  in  blast,  this  matter  presents  but  little  diffi- 
culty ;  but  if  the  furnace  is  cold,  or  newly  started,  greater  attention 
to  it  is  required.  Where  the  cinder  rises  so  high  as  to  be  seen  ap- 
proaching the  tuyere  from  below,  a  short  bar  should  be  run  into  the 
liquid  mass,  and  some  warm  cinder  drawn  over  the  dam,  after  which 
a  regular  current  of  the  cinder  will  flow  off  by  itself.  If,  in  the 
course  of  the  work — say  within  three  or  six,  or  more  hours — the 
tuyeres  begin  to  get  troublesome,  and  if  cold  or  tough  masses  begin 
to  accumulate,  and  obstruct  the  passage  of  the  blast,  the  furnace 
may  be  opened,  the  blast  taken  off,  the  stopper  removed,  and  the 
top  of  the  cinder  drawn  off,  cooled,  and  removed ;  then  some  cold 
small  coal  or  coke  may  be  thrown  over  the  hot  forehearth  ;  after 
which,  the  workmen  should  run  a  ringer  through  the  whole  length 
of  the  hearth,  from  the  damstone  to  the  back,  moving  the  point  of 
the  bar  along  the  sides,  the  bottom,  and  the  backstone;  and  if  any 
lumps  of  cinder  stick  anywhere  in  the  hearth,  they  should  be  de- 
tached, and,  by  a  slanting  motion  of  the  iron  bar,  brought  forward 
before  the  timp.  Such  an  overhauling  or  cleaning  of  the  hearth 
must  be  done  quickly.  If  the  furnace  is  not  in  good  condition,  two 
workmen  should  be  employed  on  it.  After  the  lumps  and  cold  cin- 
der are  removed,  a  little  blast  is  let  in,  to  blow  out  such  dust  and 
small  coal  as  would  obstruct  the  blast,  and  tend  to  form  more  lumps 
of  cinder.  When  the  hearth  is  thus  cleaned,  the  blast  is  taken  off, 
and  a  new  stopper  rammed  firmly  in.  This  is  effected  with  diffi- 
cul,ty,  on  account  of  the  liquid  slag  below;  but,  by  holding  a  strong 
sheet-iron  plate  between  the  timpstone  and  cinder,  it  may  be  facili- 
tated. The  blast  is  then  turned  on,  and  the  work  proceeds  as  before. 
This  kind  of  cleaning  is  more  frequently  needed  in  coke  and  stone 


190  MANUFACTURE   OF   IRON. 

coal,  than  in  charcoal  furnaces,  and  generally  where,  by  reason  of 
too  wide  a  hearth,  too  weak  or  too  strong  a  blast,  or  other  causes, 
the  furnace  is  inclined  to  make  dust  ;  for  such  dust  includes  the 
remains  of  half  smelted  ores,  which  form  with  it  infusible  lumps. 
The  toughest  clinkers  are  generally  first  formed  in  the  forehearth, 
if  the  other  part  of  the  furnace  is  in  good  order ;  to  prevent  this, 
cast  iron  plates,  all  over  the  timp  and  sides,  are  very  useful,  and 
ought  to  reach  as  low  as  possible  into  the  basin  of  the  hearth. 

o.  If  through  accident,  or  some  other  cause,  the  hearth  gets  too 
cold  ;  if  the  reduction  of  the  ores  is  imperfect,  and  the  cinders  black 
or  dark  green,  great  caution  is  required  to  obviate  difficulties ;  for 
generally,  in  that  case,  the  tuyeres  work  dark,  and  clinkers  accu- 
mulate before  them.  Our  only  resource  is  to  open  the  hearth,  and 
work  the  furnace,  however  disadvantageous  such  a  course  may  be. 
If  we  could  keep  the  furnace  closed  up,  and  apply  the  blast,  it 
would  recover,  in  most  cases,  by  itself.  But  commonly  there  ap- 
pears to  be  nothing  in  the  furnace  but  ores;  these  come  down 
rapidly,  and  sometimes  pile  up  fast,  when  no  other  resort  than  to 
open  the  hearth,  and  to  take  the  cold  stuff  out,  is  left  us.  At 
this  point  of  the  operations,  if  at  any  point,  fast  work  is  required, 
for  the  hearth  cannot  bear  any  reduction  in  temperature.  Where 
the  damstone  can  be  conveniently  lowered,  or  where  the  cinders 
can  be  kept  by  any  method  low  at  the  tuyere,  so  that  the  blast 
cannot  touch  the  surface  directly,  much  trouble  and  difficulty  will 
be  avoided. 

p.  The  tapping  of  the  iron  may  be  effected  with  comparative 
ease  at  charcoal  furnaces ;  but  at  stone  coal  furnaces,  it  is  done  with 
less  facility.  In  the  first  case,  there  is  scarcely  any  possibility  of 
failing  to  make  gray  iron  from  the  start.  This  iron  is  but  little  in- 
clined to  chill  at  the  bottom;  and  the  hearth  may  be  kept  free  of  it 
very  easily.  But  at  stone  coal  furnaces,  during  the  first  week  or 
two  weeks,  scarcely  any  gray  iron  can  be  expected :  and  the  white 
iron,  however  liquid  it  may  be,  is  very  apt  to  chill,  and  disturb  the 
tapping-hole,  which,  if  once  filled  with  cold  iron,  is  not  easily 
opened.  The  general  plan  is,  to  blow  through  the  tapping-hole 
after  the  iron  is  let -out ;  and  where  cold  iron  sticks  in  the  bottom, 
this  is  almost  the  only  means  by  which  the  cleaning  of  a  hearth 
in  stone  coal  furnaces  may  be  effected.  To  this  subject  too  much 
attention  cannot  be  paid,  because,  of  all  the  disorders  which  arise, 
chilled  iron  in  a  hearth  is  the  worst. 

q.  It  is  not  difficult  to  assign  a  reason  for  most  of  the  disorders 
•which  occur  in  a  blast  furnace.  We  shall,  therefore,  call  the  atten- 


REVIVING   OF  IRON.  191 

tion  of  the  iron  manufacturer  to  the  causes  of  some  of  them. 
Upon  the  location  of  a  furnace  a  great  deal  depends.  The  furnace 
should  be  in  a  position  where  storms  and  gales  are  not  likely  to 
affect  it.  Where  it  is  placed  against  a  hillside,  care  should  be 
taken  that  no  moisture  from  the  hill  shall  come  in  contact  with  the 
stack.  Even  a  trunnel  head  bridge  of  timber  presents  a  question- 
able advantage,  where  it  should,  through  any  circumstance,  be  the 
means  of  conducting  rain  water  to  the  stack.  Moisture  in  the 
upper  part  of  the  stack  tends  to  reduce  the  burden,  and  to  cause 
scaffolding  in  and  above  the  boshes. 

r.  A  wet  or  cold  bottom  stone  tends  to  chill  the  iron  and  cinder 
below  the  tuyere;  this  occasions  a  reduction  of  burden  and  yield, 
and  an  inferior  quality  of  metal,  besides  causing  trouble  in  keeping. 
Wet,  or  imperfectly  prepared  stock  occasions  irregularities  of  a  very 
perplexing  nature,  which  sometimes  appear  to  be  unaccountable. 

Too  weak  blast  reduces  burden  and  yield,  and  is  injurious  to  the 
hearthstones. 

Too  heavy  blast,  which  happens  less  frequently,  reduces  burden 
and  yield,  by  its  tendency  to  deposit  coal  dust  in  the  corners  of  the 
hearth,  and  on  the  top  of  the  boshes,  from  the  mechanical  destruc- 
tion of  coal.  It  facilitates  the  formation  of  lumps  and  balls  of  half- 
melted  cinder,  which  are  very  troublesome  to  the  keeper.  The  dis- 
advantages of  a  new,  or  not  perfectly  dry  stack  are  but  tempo- 
rary ;  a  heavy  stack,  that  is,  a  large  mass  of  masonry,  requires 
of  course  more  time  and  fuel  to  dry  it  than  a  small  stack. 

s.  A  furnace  should  be  filled  very  regularly ;  that  is  to  say, 
every  new  charge  of  coal  and  ore  should  just  fill  the  furnace,  and 
no  more  than  fill  it.  To  secure  this  regularity,  a  charge  measure  is 
generally  employed  at  charcoal  furnaces  with  narrow  tops.  This  mea- 
sure is  constructed  of  two  half  inch  round  iron  bars,  so  connected  at 
one  end  that  one  bar  sinks  into  the  furnace,  while  the  other  serves 

Fig.  67. 


Charge  measure. 


\ 
192  MANUFACTURE   OF  IRON. 

as  a  handle.  Fig.  67  represents  this  arrangement :  5  is  the  handle, 
and  G  the  measure;  a  little  cast  iron  plate,  a,  prevents  the  sinking  of 
the  rod  into  the  spaces  between  the  materials,  and  prevents  errors. 
At  coal  or  coke  furnaces,  or  furnaces  with  wide  tops,  this  measure  is 
unnecessary,  for  the  material  is  not  permitted  to  sink  very  low  before 
another  charge  is  filled.  Irregular  filling  produces  irregular  work,  bad 
iron,  and  small  burden,  as  well  as  trouble  to  the  keeper.  The  common 
way,  at  charcoal  furnaces,  of  filling  coal  by  the  basket,  is  a  very 
imperfect  method  of  measuring,  for  some  baskets  contain  but  two 
bushels,  while  others  contain  three  bushels,  and  even  more.  The 
English  coke  barrow  is  preferable  to  baskets,  and,  at  many  fur- 
naces, is  employed.  It  is  a  two-wheel  hand  cart,  of  the  capacity 

Fig.  68. 


Coal  barrow. 

of  twelve  or  fifteen  bushels.  It  is  represented  by  Fig.  68.  But 
where  the  stock  is  to  be  hoisted,  and  no  trunnel  head  bridge  leads 
to  the  top  of  the  furnace,  such  barrows  cannot  be  employed.  Sheet 
iron  boxes,  of  capacity  sufficient  to  contain  one  charge,  are  more 
useful  still,  both  for  coal  and  ore ;  these  boxes,  being  lifted  or 
put  on  light  wagons,  are  pulled  by  a  horse  to  the  hoisting  place,  or 
to  the  trunnel  head.  Frequently  we  find  rails  laid,  on  which  these 
sheet  iron  wagons  run  ;  these  reach  across  the  furnace  top.  But 
this  is  accompanied  with  some  difficulty,  for  if  the  road  to  the  top 
is  too  small,  the  flame  will  play  around  the  rails ;  and  a  stream  of 
water,  which  it  is  sometimes  inconvenient  to  obtain,  will  be  required 
to  cool  them.  Nevertheless,  such  boxes  and  railroads  are  very  use- 
ful, and  it  is  to  be  wished  that  they  were  more  extensively  employed. 
To  assist  in  spreading  abroad  the  knowledge  of  an  arrangement  for 
filling,  which  is  very  much  needed,  I  propose  the  following  im- 
provement, on  the  principle  of  a  railroad.  In  Fig.  69,  a  repre- 
sents the  furnace  top ;  &,  b  two  posts  of  iron  or  wood  which  carry 
the^cap  c ;  on  c  a  double  or  H  rail  of  cast  iron,  d,  is  fastened,  on 
whose  two  flanches  the  wheels  or  pulleys  e  e  run.  The  horse  shoe 
/,  /  connects  both  wheels,  and  serves  to  suspend  and  fasten  the 
sheet  iron  box  g,  which  contains  the  ore  or  coal  to  be  charged;  the 


REVIVING  OF  IRON.  193 

bottom  of  the  box  is  movable  in  two  halves,  at  the  hinges  h,  h,  and 
will,  if  opened,  drop  the  contents  of  the  box  at  any  place  where  it 
is  desired,  and  of  course,  therefore,  just  in  the  centre  of  the  furnace, 
if  wished.  The  bottom  of  the  box  may  be  altered  agreeably  to  any 

Fig.  69. 


Suspension  railroad  for  filling. 

particular  notions ;  and  the  form  of  the  box  may  also  be  altered ; 
but  we  are  inclined  to  believe  that  a  simple  square  or  round  vessel, 
with  a  movable  bottom,  will  answer  every  purpose.  Such  a  rail- 
road, sufficiently  high  to  permit  everywhere  a  free  passage  under  it, 
may  be  extended  over  the  yard,  and  may  be  made  even  movable, 
so  that  it  may  be  brought  to  the  spot  where  ore  and  coal  are  to  be 
loaded.  At  the  fastening  point,  where  the  box  is  suspended  from 
/,/,  a  kind  of  steelyard  scale  may  be  applied,  so  that  loading  and 
weighing  may  be  effected  at  the  same  time. 

Where  furnaces  are  located  in  plains,  it  is  necessary  to  hoist 
their  stock  either  on  inclined  planes,  or  in  perpendicular  towers.  A 
variety  of  plans  to  effect  this  object  have  been  designed  and  exe- 
cuted ;  but,  of  all  these,  that  most  in  use  is  one  which  was  first  in- 
troduced at  the  Crane  Works,  Pa.,  and  is  now  to  be  found  in  many 
other  establishments.  A  reservoir  of  water  is  put  upon  the  trunnel 
head  bridge,  where  it  is  kept  filled  by  means  of  force-pumps  from 
the  blast  engine  or  waterwheel.  An  iron  chain  suspended  over 
13 


194  MANUFACTURE   OF   IRON. 

a  pulley  carries  one  or  two  buckets  of  sheet  iron,  sufficiently  heavy, 
when  filled,  to  balance  a  charge  of  ore  or  coal.  "When  either  of 
these  is  loaded  below,  the  filler  turns  a  stopcock,  and  fills  the  water 
bucket  or  barrel,  which  descends  and  lifts  up  the  charge.  A 
valve  in  the  bottom  of  the  water  cask,  which  is  opened  by  a  simple 
arrangement,  permits  the  water,  when  it  arrives  at  the  proper 
place,  to  escape.  The  platform  containing  the  ore  or  coal,  re- 
lieved from  its  burden,  is  charged  with  empty  boxes  or  barrows, 
after  which  it  descends,  and  the  water  barrel  again  rises.  In  this 
way  the  duty  is  performed  where  but  one  water  cask  is  employed, 
which  is  quite  sufficient  for  one  furnace ;  but  where  two  or  more 
furnaces  are  to  be  supplied  by  the  same  mechanism,  two  water 
casks,  one  on  each  end  of  the  chain,  are  applied,  to  avoid  the  loss 
of  time  caused  by  the  descent  of  the  empty  boxes.  Sometimes  an 
endless  chain  is  applied,  by  way  of  compensation  for  the  inequality 
of  length  in  the  working  chain. 

The  filling  of  furnaces  has  been,  until  the  present  time,  a  source 
of  much  anxiety  and  doubt,  and  there  is  no  question  that  many  im- 
perfections and  disturbances  in  the  furnace  operations  are  attribu- 
table to  the  carelessness  with  which  this  has  been  attended  to.  As 
good  results  will  always  depend  more  or  less  on  the  conscientious- 
ness of  the  workmen,  even  where  the  best  arrangements  exist,  the 
plan  which  promises  most  success  is  to  employ  honest  men  for  the 
performance  of  that  work. 

t.  Coal  charges  are  most  commonly  measured,  particularly  at 
charcoal  and  coke  furnaces  ;  but  at  some  of  the  stone  coal  furnaces, 
coal  as  well  as  ore  charges  are  weighed,  a  custom  worthy  of  general 
adoption.  Whether  irregularities  by  weighing,  or  those  by  measur- 
ing, are  the  greater,  is  a  doubtful  question.  My  own  experience 
leads  me  to  decide  against  the  latter.  In  any  well-regulated 
yard,  the  charcoal  charges  by  weight  will  be  found  to  work  more 
regularly  than  those  by  measurement.  With  respect  to  coke  and 
stone  coal,  the  rule  holds  equally  good,  because,  in  the  latter  case, 
a  small  difference  in  the  measure  will  have  considerable  influence 
upon  the  amount  of  carbon  put  into  the  furnace,  and  will  con- 
sequently affect  the  operations.  Generally,  this  difficulty  is  at- 
tempted to  be  met  by  means  of  larger  charges ;  but  these  are  alto- 
gether ineffectual  for  the  purpose.  Charcoal  from  hickory  and 
maple  wood  is  nearly  twice  as  heavy  as  that  from  poplar.  If,  with 
respect  to  coke,  the  difference  is  not  so  great,  it  is  at  least  sufficient 
to  account  for  many  difficulties  in  the  furnace  operations.  The 


REVIVING  OF  IRON.  195 

weighing  of  stone  coal  is  necessary,  on  account  of  its  great  specific 
gravity. 

The  moisture  which  charcoal  absorbs  from  the  atmosphere  con- 
stitutes one  of  the  main  objections  to  weighing  it;  but  this  objec- 
tion is  not  a  solid  one,  for  the  coal  absorbs  almost  as  much  moist- 
ure within  the  first  twenty-four  hours  after  it  is  charred  and  cold,  as 
it  absorbs  during  the  following  six  months.  With  respect  to  coke 
and  stone  coal,  this  objection  does  not  apply  at  all. 

Coal  charges  are  usually  of  a  given  measure  or  weight,  and 
should  any  alteration  in  their  quantity  be  required,  this  is  effected 
in  the  charges  of  the  ore.  The  amount  of  fuel  for  one  charge 
is,  in  charcoal  or  coke,  from  ten  to  fifteen  bushels,  equal  to  from 
450  to  600  pounds,  and,  in  anthracite  furnaces,  from  600  to 
1200  pounds.  The  amount  should  be  determined  by  the  size  of 
the  top;  narrow  throats  receive  larger,  and  wide  tops  smaller 
charges.  In  estimating  the  quantity  of  coal  required,  the  quality 
of  the  ore  must  be  taken  into  consideration.  Very  refractory  ores 
work  better  with  large  than  with  small  coal  charges.  The  former 
have  a  tendency  to  raise  the  heat  in  the  hearth,  because  of  the 
interval  between  the  different  ore  charges  that  descend  into  it. 

u.  The  size  of  the  charcoal,  coke,  or  stone  coal  considerably  in- 
fluences the  working  of  a  furnace.  Coarse  coal  is  apt  to  leave  large 
spaces,  through  which  small  coal  and  small  ore  will  work  down 
to  the  hearth  in  a  condition  unfit  for  service.  This  disadvantage  is 
greater  in  low  than  in  high  stacks ;  but,  in  both  cases,  it  should  be 
avoided.  In  relation  to  coke  and  stone  coal  furnaces,  our  remark 
concerning  the  influence  of  the  size  of  coal  has  especial  application ; 
for,  as  coke  is  more  incombustible  than  charcoal,  small  coke  will  be 
more  apt  to  remain  unconsumed  in  the  furnace,  to  mix  with  unreduced 
ores,  and  to  form  with  them  lumps,  which,  descending  into  the 
hearth,  and  arriving  before  the  tuyere,  are  apt  to  form  cold  clinkers, 
of  difficult  removal.  To  avoid  fine  dust  in  anthracite  furnaces  is 
a  matter  of  great  difficulty,  because  anthracite  is  very  apt  to  fly,  or  to 
throw  off  small  bits  of  coal,  when  suddenly  exposed  to  a  high  tem- 
perature. The  surest  means  of  preventing  this  are  large  throats 
and  cool  tops,  which  will,  if  not  effectually  remove,  at  least  modify 
the  evil. 

v.  Immediately  after  a  coal  charge  is  filled,  a  charge  of  ore  is 
thrown  into  the  furnace.  The  common  and  undoubtedly  the  best 
manner  of  doing  this  is  to  weigh  the  ore,  and  if  anything  in  the 
furnace  should  go  wrong,  to  dimmish  or  increase  the  ore  charge. 


196  MANUFACTURE   OF   IRON. 

Where  small  boxes  are  used  for  filling  ore,  which  is  generally  the 
case  at  charcoal  furnaces,  they  ought  to  be  as  much  as  possible  of 
equal  weight.  On  this  account,  sheet  iron  are  preferable  to  wooden 
boxes,  because  they  do  not  absorb  moisture,  which,  in  case  of  rainy 
weather,  would  diminish  the  charge  of  ore.  The  best  of  all  is  an 
iron  box,  sufficiently  large  to  contain  a  charge.  The  filling  of  ore 
by  the  measure  should  be  repudiated  altogether.  If  this  method  is 
tolerated  in  the  case  of  coal,  it  will  not  answer  with  ore,  for  ore  is 
of  great  specific  gravity,  and  an  imperceptibly  small  quantity  may 
amount  to  more  than  the  necessary  regularity  of  the  furnace  opera- 
tions will  admit.  It  must  certainly  be  admitted  that,  in  most  in- 
stances, even  a  small  variation  in  the  charge  of  ore  cannot  be  borne 
by  a  furnace,  particularly  where  its  operations  are  carried  to  a  high 
state  of  perfection,  and  where  the  burden  is  kept  at  the  highest 
pitch.  Filling  ore  by  the  measure  is  still  more  imperfect  where 
small  boxes  are  used  than  where  the  whole  charge  is  contained 
in  one  vessel. 

w.  The  objections  made  against  too  small  or  too  large  coal  will 
apply  equally  well  against  ore  that  is  too  small,  or  sandy,  or 
too  coarse.  Low  stacks  and  small  furnaces  suffer  more  from  such 
causes  than  high  stacks,  or  furnaces  of  large  capacity.  Fine,  sandy 
ore  runs  through  the  coal  into  the  hearth,  without  being  properly 
prepared,  and  occasions  the  production  of  white  iron  and  black 
cinder;  too  coarse  ore  arrives  in  the  hearth  in  a  state  unfit  for  re- 
duction, and  of  course  unfit  to  produce  good  work. 

Wet  ores,  and  ores  that  are  either  roasted  too  hard,  or  not 
roasted  at  all,  produce  bad  results;  and  the  smaller  the  furnace, 
the  worse  the  results.     In  this  case,  even  light  ore  charges  are  not 
wholly  successful ;  while  the  application  of  strong  blast,  or  the  fast  i 
driving  of  the  charges,  only  increases,  instead  of  obviating,  the  ! 
difficulty.     Weak  blast  and  light  ore  charges  can  alone  favorably 
modify  these  accidents.     Close  attention  to  the  preparation  of  the 
ores  is  thus  seen  to  be  indispensable.    Hence,  it  is  apparent  that  too 
much  care  cannot  be  taken  in  the  proper  treatment  of  the  ore  1 
where  nature  has  not  already  done  most  of  the  work,  that  is,  by 
oxidizing  and  breaking  the  ore ;  luckily,  in  three  instances  out  of 
four,  this  is  the  case  in  our  country.     The  difficulties  arising  from 
such  disorders  are  more  serious  in  charcoal  furnaces  and  low  stacks 
than  in  coke  or  anthracite  furnaces  and  high  stacks.  Too  hard  roasted 
ores,  partly  melted  into  clinkers,  are  not  much  better  than  cinders  > 
from  the  forge  fires  or  puddling  furnaces,  and  produce  the  same  re- 


REVIVING   OF  IRON.  197 

suits.  From  these  ores  it  is  almost  impossible  to  smelt  gray  pig 
iron- 

x.  A  successful  business  is  scarcely  possible  without  a  judicious 
selection  and  admixture  of  the  smelting  materials.  Rich  ores  are 
apt  to  contain  less  foreign  matter  than  is  needed  for  the  formation  of 
a  sufficient  quantity  of  cinder  to  protect  the  hot  iron  against  the 
influence  of  the  blast ;  the  production  of  white  iron,  and  the  con- 
sumption of  more  fuel  than  is  actually  necessary  to  reduce  the  ore, 
are  the  results  of  this  deficiency.  In  this  case,  an  admixture  of 
poor  ores  will  be  found  advantageous.  Poor  ores  of  a  refractory 
nature  consume- much  coal,  and  furnish  a  small  quantity  of  iron; 
but  a  great  deal  can  be  accomplished  by  the  application  of  hot 
blast.  With  respect  to  rich  ores  and  cinder  in  small  quantity,  the 
hot  blast  is  of  but  little  advantage.  We  shall  arrive  at  a  thorough 
understanding  of  this  question  in  the  course  of  this  and  the  fol- 
lowing chapter.  We  shall  allude  here  to  those  applications  which 
were  considered  useful,  and  generally  adopted,  before  the  science 
of  mixing  ores  was  established. 

The  primary  aim  of  the  iron  manufacturer  is  to  arrive  at  per- 
fection in  the  smelting  operations,  that  he  may  be  enabled  to  pro- 
duce from  a  given  amount  of  coal  and  ore  the  largest  possible 
quantity  of  metal  of  a  definite  quality.  This  object  can  be  realized 
by  a  judicious  selection  and  mixing  of  ores;  and  where,  through 
want  of  material,  this  is  not  practicable,  by  a  proper  selection  and 
addition  of  fluxes.  Nearly  every  material  mixed  with  the  ores 
is  in  itself  more  or  less  refractory ;  but,  where  several  are  mixed 
under  proper  circumstances,  they  will  melt  together,  and  be,  to  a 
greater  or  less  extent,  liquid.  The  protoxide  and  peroxide  of  iron 
may  be  considered  infusible  by  themselves ;  but  melt  when  mixed. 
Quicklime,  clay,  sand  or  silex,  and  magnesia,  are  also  very  refrac- 
tory by  themselves.  Protoxide  of  iron  melts  readily  when  mixed 
with  silex  or  clay ;  and  forms,  with  these  substances,  a  very  liquid 
cinder,  in  forge  fires  and  puddling  furnaces.  Lime  and  magnesia 
melt  together  with  silex,  but  require  a  very  high  temperature.  If, 
however,  a  little  clay  is  added  to  the  mixture,  the  melting  is  facili- 
tated; and  if  a  small  portion  of  the  oxides  of  iron  is  added,  the 
mixture  will  flux  at  a  still  lower  temperature.  These  observations 
can  be  made  at  a  coke  or  anthracite  furnace.  Potash  and  silex 
melt  readily  together;  so  also  do  soda  and  silex,  or,  what  is  the 
same  thing,  sand  and  soda;  but  a  mixture  of  potash,  soda,  and  sand 
melts  with  greater  facility.  If  we  add  potash  or  soda,  or  both,  to 


198  MANUFACTURE   OF   IRON. 

the  above  mixture  of  lime,  magnesia,  and  silex,  the  melting  point 
of  the  whole  will  be  lowered  ;  this  is  somewhat  remarkable,  because 
the  sand  or  silex  can  be  increased  in  a  greater  ratio  than  the  potash 
and  soda.  From  this  it  follows  that  the  greater  the  number  of  ele- 
ments in  furnace  cinder,  the  more  easily  the  cinder  will  flow ;  or,  in 
other  words,  that  the  more  we  mix  and  multiply  the  kinds  of  ore, 
the  more  regularly  the  cinder  will  flow.  Silicious  ores,  calcareous 
ores,  and  clay  ores  are,  singly,  very  refractory  and  troublesome  in 
the  furnace.  Ore,  mixed  principally  with  silex,  requires  a  high 
temperature  to  produce  iron,  on  account  of  the  refractory  nature 
of  the  admixture.  But  it  will  readily  make  gray  iron.  Calcareous 
ore,  or  iron  ore  mixed  with  lime,  is  equally  refractory  by  itself, 
requires  a  high  heat  for  smelting,  and  is  inclined  to  make  white  iron. 
Clay  ores  are  not  very  refractory;  if  no  lime  or  potash  is  present, 
or,  if  the  ores  are  not  very  rich,  they  do  not  make  iron  at  all,  or 
make  it  in  very  small  quantity;  for  a  great  deal  of  the  iron  is  con- 
sumed in  fluxing  the  clay.  If  we  mix  calcareous  and  silicious  ores 
together,  they  will  not  only  produce  iron  with  greater  facility  than 
each  would  separately  produce  it,  but  they  work  with  less  coal ; 
and  if  to  this  mixture  we  add  an  ore  belonging  to  the  aluminous  or 
clay  ores,  the  operations  in  the  furnace  will,  in  every  respect,  prove 
still  more  satisfactory.  There  are  many  more  admixtures,  as  may 
be  presumed,  which  influence  the  manufacture  of  iron;  but  the  above 
constitute  the  main  body  of  foreign  matter  mixed  with  iron  ores. 

If,  through  the  influence  of  local  causes,  we  are  unable  to  obtain 
such  a  mixture  of  ore  as  will  satisfy  us,  we  are  compelled  to  add 
such  foreign  matter  as  will  produce  satisfactory  results.  Purely 
silicious  ores  will  require  an  addition  of  clay  ore  and  pure  limestone, 
or,  if  no  clay  ore  can  be  obtained,  argillaceous  limestone;  and  if 
the  latter  cannot  be  had,  any  mixture  of  clay  and  iron,  even  blue 
clay,  will  answer.  Fire  clay,  or  any  pure  clay  without  iron,  we 
cannot  recommend ;  but,  if  it  is  necessary  to  make  use  of  such 
material,  it  will  be  advisable  to  dissolve  it,  and  to  mix  it  well  with 
fine  ore.  Limestone  or  calcareous  ores  require  the  addition  of  sili- 
cious and  clay  ore;  and  if  these  cannot  be  obtained,  ferruginous 
shale,  which  generally  contains  both  silex  and  clay,  will  answer. 
But  this  shale  is  to  be  roasted  like  ore,  because  it  frequently  contains 
sulphurets  of  iron  (iron  pyrites).  Clay  ores  generally  contain  so 
much  silex,  that  no  addition  of  sand  or  silicious  ore  is  needed. 
For  these,  lime  is  a  sufficient  flux.  It  is  a  common  practice  to 
flux  the  ores,  for  which  purpose  limestone  is,  in  this  country,  in 


REVIVING   OF  IRON.  199 

most  instances  employed,  because  the  main  body  of  the  ores  are  of 
a  silicious  and  clayey  nature.  But  if,  in  the  case  of  silicious  ore, 
an  argillaceous  or  magnesian  limestone,  and,  in  the  case  of  clay  ore, 
a  silicious  limestone,  be  selected,  the  result  will  be  highly  favor- 
able. In  all  cases  where  limestone  or  any  other  flux  contains  a  little 
iron,  the  smelting  operations  will  be  facilitated ;  and  a  mixture  of 
ore  will  produce  the  most  perfect  work.  The  addition  of  dead 
fluxes  is  thus  rendered  unnecessary.  We  cannot  too  much  insist 
upon  the  importance  of  this  subject,  for  upon  it  depend,  .to  a 
greater  or  less  extent,  the  quality  and  quantity  of  the  metal,  and 
in  consequence  the  success  of  the  business.  There  is  a  point  where 
the  liquidity  of  the  slag  ceases  to  be  of  advantage.  Ores  which  con- 
tain feldspar,  as  is  generally  the  case  with  the  magnetic  ores,  flux, 
in  most  instances,  too  readily ;  in  which  case,  a  more  refractory 
material,  such  as  silex  or  clay,  is  to  be  added.  The  silicious  ores 
of  Eastern  Pennsylvania  require  a  large  amount  of  lime;  but  where 
clay  ores  can  be  added  to  the  lime,  as  in  Huntingdon  county,  they 
work  exceedingly  well.  The  Eastern  States  do  not,  in  this  respect, 
enjoy  equal  advantages  with  the  Western  States.  In  fact,  from  the 
eastern  boundary  of  Pennsylvania  to  the  western  boundary  of  Ar- 
kansas and  Missouri,  the  coal  measures — to  a  greater  or  less  extent 
everywhere  accessible — contain  this  material  in  abundance. 

Where  small  boxes  are  in  use  for  filling  and  weighing  ore,  the 
distinct  separation  of  the  ores  and  flux  is  a  matter  of  no  difficulty ; 
but  where  only  one  box  is  used  for  the  whole  mixture,  much  atten- 
tion is  required.  The  flux,  as  well  as  the  ore,  should  be  filled  by 
weight;  not,  as  frequently  done,  thrown  in  at  random  by  the  shovel. 
For,  let  it  be  well  remembered  that  the  quantitative  mixture  of  ore, 
or  ore  and  flux,  is  definite ;  it  is  not  a  matter  of  indifference,  in  seek- 
ing to  obtain  the  best  result,  how  much  we  take  of  one  kind  of  ore 
and  how  much  of  another,  or  how  much  limestone  or  flux  we  use. 
Too  great,  is  as  injurious  as  too  small,  a  quantity  of  limestone.  If 
the  quantities  of  ore  and  flux  are  determined,  it  is  a  good  practice 
to  mix  all  the  ores  previous  to  being  weighed.  This  mode  of  mix- 
ing the  ores  has  from  time  immemorial  been  practiced  in  Germany. 
It  increases  to  a  small  degree  the  labor  of  the  yard,  but  richly  repays 
this  labor  in  the  better  work  of  the  furnace.  The  process,  called 
by  the  Germans  Moellerung,  is,  simply  to  spread  on  some  level 
place  a  certain  quantity,  say  one  hundred  wheelbarrowsfull,  of  one 
kind  of  ore;  upon  this,  half  that  quantity  of  another  kind;  upon 
the  latter,  one-fifth  or  one-sixth  that  quantity  of  a  third  kind;  and 


200  MANUFACTURE   OF  IRON. 

over  the  whole,  the  limestone  or  flux,  if  any  is  needed.  Beds  from 
one  to  two  feet  in  height  are  prepared  in  this  way,  from  which  an 
amount  sufficient  for  a  charge  is  taken.  The  mixing  of  the  ores 
can,  in  this  manner,  be  watched,  without  the  necessity  of  intrusting 
its  management  to  unthinking  workmen. 

The  ore  should  be  spread  uniformly  over  the  coal  in  the  furnace; 
but  where  the  blast  is  weak,  or  the  ores  wet  and  earthy,  it  maybe 
advisable  to  pile  the  ore  in  the  middle  of  the  throat,  that  the  rising 
gases  may  escape.  This  should  be  avoided,  if  possible,  on  account 
of  the  coal  consumed.  Furnaces  which  have  but  one  charging 
place,  are  often  badly  managed,  because  the  fillers  either  charge  in- 
discriminately on  either  side,  or,  what  is  still  worse,  one  fille'r  is 
in  the  habit  of  throwing  the  stock  to  one  side,  and  the  filler  of  the 
next  turn  to  the  other  side.  These  irregularities  give  rise  to 
changeable  work  in  the  hearth,  to  the  formation  of  lumps  in  the 
hearth  and  boshes,  and  finally,  what  is  generally  the  case  when 
the  furnace  is  well  heated,  to  scaffolding  in  and  above  the  boshes, 
which,  of  course,  is  likely  to  be  attended  with  serious  consequences. 

Ores  which  contain  zinc,  arsenic,  or  chlorides  are  apt  to  scaffold, 
at  some  point  of  the  upper  part  of  the  in-wall,  in  charcoal  furnaces. 
In  this  respect,  stone  coal  or  coke  furnaces  are  in  no  danger. 
For  this  evil,  small  coal  charges  and  a  hot  top  are  the  best  reme- 
dies. Sufficiently  wide  throats,  and  the  heating  of  the  ore  in  the 
middle  of  the  coal,  are  required,  to  keep  the  lining  as  warm  as  pos- 
sible, and  to  permit  the  evaporated  metals  to  escape. 

y.  The  number  of  charges  brought  down  in  twelve  or  twenty- 
four  hours,  or  the  quantity  of  iron  produced,  depends  very  much  on 
the  amount  of  blast  sent  into  the  furnace.  Nevertheless,  we  may 
remark  that  the  quantity  of  air  does  not  determine  with  certainty 
the  descent  of  charges,  or  the  quantity  of  iron  made.  A  cold  hearth 
never  produces  so  much  iron  as  a  properly  heated  furnace,  where 
the  blast,  in  both  instances,  is  the  same.  If  the  hearth  is  too  warm, 
nearly  the  same  difficulty  occurs.  A  liquid,  lively  cinder  makes  a 
far  greater  quantity  of  iron  with  a  given  amount  of  blast,  than  a 
tough,  chilly  cinder.  Cold,  black,  or  dark  green  cinder  produces 
still  less  iron,  and  is,  on  the  whole,  the  least  advantageous.  A 
clean  hearth,  free  of  clinkers  and  cold  iron,  is,  of  all  others,  the 
most  likely  to  produce  good  metal,  and  in  abundant  quantity. 

z.  The  question,  what  number  of  tuyeres  it  is  most  profitable  to 
us©  in  a  furnace,  it  is  difficult  to  answer.  It  can  be  decided  only 
by  experience.  Nevertheless,  we  shall  present  some  conclusions 


REVIVING   OF  IRON.  201 

drawn  from  experience.  Where  cold  blast  is  used,  we  should  be 
in  favor  of  never  applying  more  than  two  tuyeres,  and  of  trying 
very  hard  to  do  with  one ;  but  where  hot  blast  is  used,  two  or 
even  more  tuyeres  are  almost  indispensable,  for  the  following  rea- 
sons :  In  the  smelting  process  by  cold  blast,  as  strong  a  pressure  in 
blast  as  the  fuel  will  possibly  bear  is  highly  advantageous.  This 
fact  favors  the  use  of  as  few  tuyeres  as  possible,  for,  if  heavy 
pressure  is  applied,  the  more  tuyeres  we  have,  the  more  coal  we 
destroy.  In  addition  to  this,  the  dust  in  the  hearth  and  boshes  in- 
creases. With  hot  blast  the  matter  is  different.  There  is  no  need 
of  pressure ;  and  by  the  tendency  of  the  hot  air  to  combine  more 
readily  with  the  coal,  small  coal,  which  does  not  burn  well,  is  very 
apt  to  gather  in  the  corners  of  the  hearth,  and  produce  difficulties 
that  are  well  known.  Therefore,  the  same  reasons  which  are  in 
favor  of  as  few  tuyeres  as  possible  with  cold  blast,  are  in  favor  of 
as  many  as  possible  with  hot  blast. 

It  is  sometimes  the  case  that  the  gray  iron  from  the  furnace  is 
directly  used  for  foundry  purposes,  such  as  to  cast  hollow  ware, 
stove  plates,  &c.  This  mode  of  making  use  of  the  hot  metal  is 
practiced  only  at  a  few  small  charcoal  furnaces.  In  many  respects, 
this  is  a  bad  practice,  and  should  be  avoided.  The  disturbance 
which  it  occasions  to  the  smelting  operations  more  than  counter- 
balances the  advantage  gained ;  and,  besides,  the  castings  of  re- 
melted  iron  are  preferable  to  those  cast  directly  from  the  furnace. 

aa.  The  time  at  which  the  iron  should  be  let  out  is  generally  so 
arranged  that  the  workmen,  changing  every  twelye  hours,  have  each 
their  cast ;  where  the  hands  work  by  the  job,  they  generally  stay 
from  one  cast  to  the  other,  a  period  frequently  of  twenty-four  hours, 
if  the  furnace  is  newly  blown  in,  or  if  any  disturbance  happens. 
The  preparation  of  the  pig  bed,  moulding  of  pigs,  is  the  duty  of 
the  keeper,  or,  at  large  furnaces,  of  the  helper,  or  second  keeper. 
The  founder  generally  assumes  the  duty  of  tapping  the  iron.  Six 
in  the  morning,  and  six  in  the  evening  is  the  time  usually  set  apart 
for  casting. 

bb.  If  the  melted  iron  remains  too  long  in  the  furnace,  it  is  very 
apt  to  turn  white,  on  account  of  the  action  of  the  blast.  Such  an 
accident  should  be  avoided,  for  it  is  injurious  both  to  the  furnace 
and  to  the  iron.  But  in  charcoal  furnaces,  the  inconvenience  is  not 
so  great  as  in  anthracite  and  coke  furnaces.  If,  in  an  anthracite 
furnace,  the  cinder  rises  too  high,  it  is  very  apt  to  adhere  in  lumps 


202  MANUFACTURE    OF  IRON. 

to  the  hearthstones  ;  after  the  iron  is  let  out,  we  are  forced  to  break 
away  these  lumps  with  great  caution.  In  charcoal  furnaces,  how- 
ever, the  action  of  the  blast  is  frequently  resorted  to  for  the  produc- 
tion of  white  iron  for  the  forges ;  and  should  the  original  iron  have 
been  gray,  or  mottled,  a  strong  forge  iron  is  produced.  At  many 
European  furnaces,  where  forge  metal  is  manufactured,  the  desired 
effect — that  is,  the  production  of  white,  strong  metal,  with  the  least 
expenditure  of  coal — is  obtained  by  some  secret  method  of  twist- 
ing and  dipping  a  tuyere.  This  manoeuvre,  at  the  wiilf  Js  oven 
and  the  blue  oven,  is  applied  to  the  ores  of  the  primitive  and  tran- 
sition formation,  as  spathic  and  magnetic  iron  ores.  It  would  be 
of  no  use,  in  this  country,  at  places  where  oxides  for  the  production 
of  gray  iron  are  principally  smelted.  Where  white  iron  is  smelted 
by  a  high  tuyere,  or,  what  is  the  same  thing,  where  the  iron  cannot 
be  reached  by  the  free  oxygen  of  the  blast ;  and  where  it  is  smelted 
by  a  weak  blast,  or  a  too  wide  hearth,  it  is  always  bad,  weak,  does 
not  yield  well,  and  does  not  make  good  wrought  iron. 

cc.  If  no  accidents  or  disturbances  happen  in  the  regular  furnace 
operations,  and  if  everything  is  in  proper  order,  the  quality  of  the 
metal,  that  is,  its  amount  of  carbon,  is  entirely  dependent  upon  the 
burden.  Small  burden  will  produce  gray,  and  heavier  burden 
white  iron.  In  the  former  case,  the  furnace  will  be  inclined  to 
dry  the  cinder,  that  is,  to  deposit  balls  in  the  hearth,  by  which 
the  hearth  is  cooled,  and  the  temperature  frequently  brought  so 
low  as  to  produce  a  tendency  towards  the  other  extreme,  that  is, 
black  or  dark  green  cinder  with  white  iron.  Such  changes  are 
very  disadvantageous,  and  should,  by  all  means,  be  avoided.  A 
well-conducted  furnace  should  never  be  too  heavily,  and  never  too 
lightly  charged,  for  one  extreme  is  as  bad  as  the  other.  A  medium 
course  is  the  most  profitable,  that  is,  to  make  mottled  iron,  and  trust 
to  accident  for  the  manufacture  of  gray  or  white  iron  ;  for  both,  in 
certain  cases,  will  be  produced,  In  this  way  the  furnace  will  carry 
the  heavier  burden,  and  the  result  will  be,  in  either  case,  a  good 
forge  metal. 

White  iron  is  produced  by  a  cold  furnace ;  but  it  can  be  made 
by  a  hot  furnace.  The  white  iron  of  too  heavy  burden  always 
proves  a  good  forge  iron ;  but  the  white  iron  of  too  light  burden 
is  of  a  very  doubtful  nature,  and  in  most  instances  is  bad,  if  smelted 
from  the  ores  of  the  coal  formation.  It  is  very  bad,  if  made  by 
hot  blast,  anthracite,  or  coke.  The  making  of  white  iron  can  be 
prevented  only  by  carrying  as  heavy  a  burden  as  possible. 


REVIVING   OF  IRON.  203 

dd.  The  mixture  of  ore  and  flux  is,  with  respect  to  the  quality  of 
the  metal,  a  matter  of  great  importance,  for  too  much  lime  will, 
under  all  conditions,  produce  white  iron.  If  the  hot  slag,  as  it  flows 
from  the  furnace,  blazes,  and  gets  spongy  like  pumice  stone  when 
sprinkled  with  water,  we  may  conclude  that  lime  exists  in  too  great 
quantity  in  the  charge;  but  if  the  cinder  appears  of  a  dark,  black, 
or  green  color,  even  after  the  temperature  in  the  hearth  is  raised; 
and  if  the  slag  in  the  furnace,  in  spite  of  the  heat,  is  inclined  to 
form  balls,  to  blacken  the  tuyere,  and  to  stick  to  the  hearthstones, 
we  may  conclude  there  is  not  sufficient  lime  in  the  charge.  Clay 
ores  are  very  apt  to  clinker  before  the  tuyere,  even  where  an  abund- 
ance of  limestone  is  present;  but  the  limestone  may  be  diminished 
by  the  application  of  hot  blast.  If  the  composition  of  the  ores  is 
such  as  by  itself  to  make  a  very  liquid  cinder — which,  with  bog 
ore,  shell  ores,  or  calcareous  ores,  is  frequently  the  case — we  must 
not  expect  gray  iron,  until  with  this  composition  we  mix  silicious 
ore.  Silicious  ore  is  highly  favorable  to  the  manufacture  of  gray 
iron ;  in  fact,  foundry  iron  can  hardly  be  made  without  it.  To  pro- 
duce such  iron,  a  strong  cinder  and  a  hot  furnace  are  required.  The 
least  disturbance  which  tends  to  cool  the  furnace  will  cool  the  tough 
cinder,  and  in  this  way  often  produce  very  troublesome  scaffoldings 
in  the  hearth  or  boshes. 

ee.  The  color  of  the  cinders  is  not  a  safe  criterion  by  which  we 
may  estimate  the  working  of  the  furnace.  Gray  cinders  may  con- 
tain as  much  iron  as  green  or  black  cinders.  But,  as  a  general 
rule,  the  former  indicate  better  work  than  the  latter.  Where  the 
charcoal  furnace  is  in  good  condition,  they  are  generally  well 
glazed,  transparent,  and  of  a  greenish  color.  Perfectly  gray,  spongy, 
white,  and  black  or  olive-green  cinders  are  not  the  most  favorable 
indications  at  a  charcoal  furnace.  Anthracite  and  coke  furnaces, 
when  well  conducted,  generally  furnish  a  gray,  stony-looking  cin- 
der, but  always  well  glazed.  In  these  furnaces,  spongy,  or  green, 
or  black  cinders  are  almost  as  unfavorable  indications  as  in  char- 
coal furnaces.  Those  which  lose  their  glazing,  or  fall  to  pieces, 
by  being  exposed  to  the  influence  of  the  atmosphere,  contain  too 
much  lime,  and  never  fail  to  make  white  iron  of  inferior  quality. 
That  their  color  is  no  indication  of  the  quality  of  the  metal,  is  evi- 
dent; for  the  ore  or  coal  may  contain  the  oxides  of  other  metals, 
which  generally  produce  various  shades.  Variegated  cinders,  like 
agate,  indicate  that  the  ore  or  flux  employed  is  too  coarse,  or,  what 
is  still  worse,  that  there  is  scaffolding  in  the  furnace.  Small  stacks, 


204  MANUFACTURE  OF  IRON. 

or  narrow  hearths,  are  endangered  when  they  work  coarse  ore.  In 
a  large  anthracite  furnace  with  a  wide  hearth,  so  much  pains  need 
not  be  taken  in  breaking  the  stock,  for  there  is  scarcely  a  possibility 
of  choking  or  scaffolding  such  a  furnace. 

ff.  If  any  accidents  occur,  such  as  scaffolding  below  or  above 
the  tuyere,  or  in  lining,  it  is  a  bad  practice  to  throw  in  at  the 
tuyere  materials  either  to  flux  or  to  heat  the  furnace.  Lumps  and 
cold  cinders  below  the  tuyere  can  be  far  more  easily  removed  by 
means  of  the  bars  and  ringers  than  by  means  of  fluxes  thrown  into 
the  tuyere,  or  thrown  below  the  timp;  for  the  addition  of  fluxes 
does  nothing  more,  at  best,  than  to  remove  the  lumps  where  they 
are  the  least  troublesome.  Scaffolding  above  the  tuyere,  when  it 
impedes  the  blast,  or  the  descent  of  charges,  is  to  be  removed  by 
the  withdrawal  of  the  ore  charges;  and,  if  considered  dangerous, 
by  sinking  the  materials  in  the  furnace  to  a  point  very  near  or  above 
the  boshes,  and  melting  away,  by  means  of  scrap  iron  with  lime- 
stone, as  in  a  cupola,  any  obstruction  in  the  hearth  or  boshes.  All 
difficulties  may  thus  be  removed  in  a  very  short  time.  Obstructions 
which  endanger  the  progress  of  the  smelting  operations,  by  so 
choking  or  chilling  the  hearth  that  coal  cannot  descend,  are  the  re- 
sults of  inexcusable  neglect — inexcusable  both  to  the  manager  and 
to  the  workmen.  Charcoal  furnaces  are  but  little  exposed  to  such 
disorders:  but  coke  and  anthracite  furnaces  are  very  much  exposed 
to  them,  if  they  smelt  gray  iron;  for,  in  the  manufacture  of  this 
iron,  a  narrow  hearth  and  strong  cinder  are  required.  When,  in 
such  furnaces,  the  least  disturbance  takes  place,  the  cinder  is  very 
apt  to  stick  to  the  boshes  or  hearth,  and  a  green,  and  at  last  a  black, 
cinder  and  white  iron  are  produced.  So  long  as  the  cinder  is  only 
of  a  light  green  color,  or  streaked  with  green,  no  danger  need  be 
apprehended,  and  the  furnace  maybe  considered  in  good  condition; 
but  so  soon  as  brownish  streaks  in  the  cinder  appear,  the  furnace 
should  be  watched.  If  the  brown  color  does  not  disappear  within 
five  or  six  hours,  it  is  advisable  to  diminish  the  ore  charges,  for  this 
color  deepens  so  rapidly,  that  within  twenty-four  hours  the  cinder 
will  become  black.  If  light  charges  should  not  be  near  at  hand, 
the  difficulties  would  thus  be  greatly  augmented. 

gg.  The  flame  of  the  trunnel  head,  as  well  as  that  of  the  timp, 
is  indicative  of  the  nature  of  the  operations  in  the  furnace.  At 
charcoal  and  coke  furnaces,  a  heavy,  dark  top  flame  indicates  that 
the  furnace  is  cold,  and  that  the  burden  is  too  heavy.  A  bright 
smoky  flame,  which  throws  off  white  fumes,  indicates  a  too  liquid 


REVIVING   OF  IRON.  205 

cinder ;  that  too  much  limestone  is  present;  or  that  the  burden  is  too 
light.  If  the  iron  is  gray,  the  burden  can  be  increased ;  but  if  it  is 
white,  this  should  be  done  cautiously.  The  withdrawal  of  a  por- 
tion of  the  limestone  will  generally  cure  the  evil,  if  the  iron  is 
white ;  but  if  it  is  gray,  heavier  burden  is  required.  An  almost 
invisible,  lively  flame  at  the  top  is  significant  of  a  healthy  state 
of  the  furnace.  The  strength  of  the  top  flame  of  an  anthracite 
furnace  is  proportionate  to  the  amount  of  hydrogen  the  coal  con- 
tains; and  therefore  this  is,  at  best,  but  an  uncertain  indication  of  the 
state  of  the  furnace.  If  the  flame  appears  to  be  struggling  to  break 
through  the  timp,  we  may  be  sure  that  there  is  something  wrong  in 
the  interior.  But  this  depends  upon  the  ore  and  coal,  upon  the  form 
of  the  stack,  and  upon  the  blast.  It  is  common  where  small  ore  is 
used,  and  where  the  hearth  and  top  are  narrow.  The  color  of  the 
timp  flame  is,  like  that  of  the  top  flame,  indicative  of  the  work  in 
the  furnace;  and  the  rules  applicable  to  the  one  are  applicable  to 
the  other.  The  color  of  the  flame  will  be  more  or  less  modified,  ac- 
cording to  the  foreign  matter  the  ore  contains.  If  it  contains  zinc, 
arsenic,  and  lead,  the  flame  will  always  emit  white  fumes,  whether 
the  furnace  be  cold  or  warm.  If  the  materials  contain  common 
salt,  the  flame  will  emit  fumes  of  the  same  color.  "Where  the  flame 
wavers,  that  is,  where  it  is  sometimes  large  and  sometimes  small, 
there  is,  without  doubt,  scaffolding  in  the  lining.  In  this  case, 
close  watching  of  the  sinking  of  the  charges  is  needed.  If  it  is 
found  that  all  is  not  right,  a  reduction  of  the  burden  and  an  in- 
crease of  blast  must  be  resorted  to. 

M.  The  gray  metal,  where  the  operation  has  been  good,  is  very 
liquid;  and  ke"eps  liquid  for  a  long  time  in  thepig^bed.  If  of  good 
quality,  it  is,  even  in  the  thinnest  leaf,  perfectly  gray  ;  but  if  in- 
clined to  white,  the  corners  of  the  pigs,  and  thin  castings,  will  be 
white.  This  iron  appears  perfectly  white  when  liquid ;  while  white 
metal  is  of  a  somewhat  reddish,  yellowish  color,  and  throws  out 
sparks.  White  metal  chills  very  soon  in  the  moulds,  and  assumes  a 
rough,  concave  surface;  it  adheres,  with  much  tenacity,  to  the 
iron  tools  used  for  cleaning  the  hearth.  If  metal  contains  sulphur, 
it  is  very  apt  to  throw  off  fumes  of  sulphurous  acid,  or  sulphuretted 
hydrogen.  It  throws  off  sulphurous  acid,  if  smelted  by  coke  or 
coal,  and  neutral  or  proper  cinder ;  and  sulphuretted  hydrogen,  if 
lime  is  used  in  large  quantity,  which  is  generally  the  case,  because 
such  iron  cannot  be  smelted  without  an  excess  of  limestone.  Phos- 
phorus can  be  detected  only  by  an  analysis  of  the  metal. 


206  MANUFACTURE   OF  IRON. 

eV.  After  the  metal  in  the  moulds  is  cooled,  it  is  to  be  removed, 
weighed,  and  stored;  and  the  sand  of  the  pig  bed  dug  up,  wetted,  and 
prepared  for  another  cast.  The  cinders  at  small  furnaces  are  easily 
removed  in  common  carts.  At  stone  coal  furnaces,  various  methods 
have  been  devised  to  remove  the  large  mass  of  cinder  daily  pro- 
duced, of  which  that  at  present  generally  practiced  at  the  anthra- 
cite furnace  may  be  considered  the  best.  It  is  this:  Dig  two  round 
basins  of  about  five  or  six  feet  in  diameter,  and  two  feet  in  depth, 
at  the  side  of  the  stack.  In  the  centre  of  each  basin  put  a  piece 
of  pig  metal,  in  an  upright  position.  Around  this  pig  metal,  the 
cinders,  which  run  into  the  basin,  gather.  A  chain  attached  to  a 
crane  is  then  fastened  to  the  pig  metal,  by  means  of  which  the 
cold  cinder  is  placed  upon  any  suitable  vehicle,  to  be  carried  off. 

A  whole  volume  might  be  written  without  exhausting  what  could 
be  said  on  the  management  of  furnaces,  and  of  blast  furnaces  in 
particular.  But  our  space  is  limited,  and  we  wish  to  avoid  pro- 
lixity. Many  occasions  will  arise,  in  the  course  of  this  work, 
which,  we  hope,  will  enable  us  to  supply  whatever  deficiency  our 
statements  may,  thus  far,  have  exhibited. 

X.   Theory  of  the  Blast  Furnace. 

It  would  be  inconsistent  with  our  object  to  enter,  with  scientific 
minuteness,  upon  this  branch  of  our  investigations.  If  we  shall  be 
able  to  convey  to  an  intelligent  mind  a  clear  and  comprehensive 
view  of  the  operations  which  take  place  in  the  interior  of  the  blast 
furnace,  our  design  will  be  accomplished.  It  is  evident  our  expla- 
nations must  be  somewhat  of  a  speculative  nature  ;  but  these  are 
illustrated  and  confirmed  by  operations  performed  under  the  cogni- 
zance of  our  senses.  In  the  previous  chapters,  we  have  related  and 
reasoned  upon  matters  which  can  be  tangibly  verified;  but  in  the 
present  instance,  we  are  obliged  to  draw  general  conclusions  from 
isolated,  though  well-established  facts,  by  means  of  pure  analogy 
— an  operation  frequently  and  daily  needed,  and  constantly  per- 
formed by  those  engaged  in  the  management  of  blast  furnaces. 

a.  In  the  second  chapter,  we  have  spoken  of  fuel  and  its  combus- 
tion, as  well  as  of  the  different  combinations  which  oxygen  forms 
with  fuel.  We  are  forced  to  refer  to  that  subject  in  the  present  in- 
stance, for  the  process  of  combustion  must  be  well  understood  be- 
fore we  can  understand  the  chemical  operations  which  take  place 
in  a  blast  furnace.  The  fuel  used  in  the  blast  furnace  is  composed, 
to  a  greater  or  less  degree,  of  carbon,  hydrogen,  sulphur,  and  ashes. 


REVIVING   OF  IRON. 


207 


Fig.  70. 


If  oxygen  or  atmospheric  air  combines  with  carbon,  the  result  is 
either  carbonic  oxide  or  carbonic  acid;  at  a  high  temperature,  with 
a  sufficient  supply  of  air,  always  carbonic  acid.  A  suffocated  com- 
bustion, with  an  excess  of  fuel,  generally  produces  carbonic  oxide. 
The  result  of  the  combustion  of  hydrogen  and  oxygen  is  always 
water ;  that  of  the  combustion  of  sulphur  and  oxygen  always  sul- 
phurous acid. 

b.  Combustion  in  a  blast  furnace 
is,  as  may  well  be  expected,  of  a 
somewhat  complicated  nature,  and 
requires   illustration  to   be  under- 
stood.    Fig.  70  represents  a  sec- 
tion of  a  blast  furnace  in  operation, 
filled  with  coal,  ore,  and  fluxes.    If 
we  introduce  at «,  a,  the  tuyere  holes, 
a  current  of  air  or  blast,  combus- 
tion in  the  lower  part  will  ensue ; 
and,    according   to   circumstances, 
the  product  will  be  carbonic  acid  of 
greater  or  less  durability.     But  if 
we  have  an  excess  of  fuel,  and  a 
limited  supply  of  air,  the  final  pro- 
duct of  the  combustion  will  be  car- 
bonic oxide.     The  primitive  or  im- 
mediate combination  of  carbon  and 
oxygen  at  the  tuyere  forms  carbonic 
acid ;  and  this  carbonic  acid,  in  its 
progress  through  the  coal,  combines 
with  more  carbon,  and  forms  car- 
bonic oxide.     Carbonic   acid   can- 
not combine  with  any  more  oxygen  than  it  already  possesses ;  but 
carbonic  oxide  will  combine  with  as  much  more  as  it  already  con- 
tains.    Carbonic  acid  is  of  no  use  in  reviving  iron  from  the  ore,  for 
the  ore  is  a  combination  of  iron  and  oxygen ;  and  carbonic  acid 
could  not  abstract  any  oxygen  from  the  ore.     But  carbonic  oxide 
will  combine  with  whatever  oxygen  is  present  in  the  interior  of  the 
blast  furnace. 

c.  Practical  investigation  has  demonstrated  that  the  more  friable 
and  tender  the  coal  is,  the  more  easily  oxygen  combines  with  it ; 
and  that  the  more  compact  it  is,  that  is,  the  greater  its  specific 
gravity,  the  greater  is  the  difficulty  with  which  it  combines  with 
oxygen.    Heated  air  combines  more  readily  with  fuel  than  cold  air, 


Theory  of  the  blast  furnace 
illustrated. 


208  MANUFACTURE   OF  IRON. 

and  of  course  is  more  inclined  to  form  carbonic  oxide.  Soft,  open 
fuel  and  heated  air  form  carbonic  oxide,  the  agent  in  the  reduction 
of  the  ore,  more  readily  than  hard  coal;  and  we  may  conclude  that 
charcoal  and  coke  are  more  useful  than  anthracite  coal  in  the 
manufacture  of  iron.  According  to  this  statement,  the  atmo- 
sphere of  oxygen  and  carbonic  acid  will  be  a  zone  of  greater  or  less 
radius,  of  which  the  mouth  of  the  tuyere  is  the  centre,  as  the  cir- 
cular lines  in  the  engraving  indicate.  The  radius  of  this  zone  has 
been  found,  by  experiments  made  on  furnaces,  to  vary,  according 
to  fuel  and  blast,  from  six  inches  to  four  or  more  feet.  Applying 
what  we  have  said  to  a  common  furnace,  with  grate  and  draft,  the 
column  of  carbonic  acid  will  be  from  six  inches  to  four  feet  in 
height,  if  we  pass  a  current  of  atmospheric  air  through  hot  and  burn- 
ing fuel.  If  the  column  of  fuel  is  higher  than  this,  the  carbonic 
acid  will  be  gradually  converted  into  carbonic  oxide.  This  process 
is  exactly  the  same  in  the  blast  furnace ;  the  oxygen  of  the  atmo  • 
sphere  is  gradually  converted  into  carbonic  acid,  carbon  with  much 
oxygen — and  then  gradually  into  carbonic  oxide,  carbon  with  less 
oxygen.  Where  the  atmosphere  of  carbonic  acid  ceases  in  the  blast 
furnace,  we  may  conclude  that  the  working  of  the  carbonic  oxide 
upon  the  ores  commences,  and  that  it  changes  more  or  less  in  its 
course  upwards.  The  ascending  current  of  the  gases,  in  a  blast 
furnace,  consists,  then,  of  carbonic  oxide,  hydrogen,  and  combina- 
tions of  hydrogen  and  carbon.  These  latter  gases  are  derived 
directly  from  the  fuel,  above  the  reach  of  free  oxygen,  and  constitute 
gaseous  combustibles,  ready  to  unite  with  oxygen.  Mixed  with  the 
above  are  steam,  carbonic  acid,  and  nitrogen — incombustible  gasetf 
which  have  not  the  least  influence  upon  the  ore.  The  nitrogen  is 
derived  from  the  atmosphere. 

The  ascending  current  of  the  gases  from  the  tuyeres  differs  in 
composition  according  to  height ;  of  course  this  composition  will 
not  be  alike  at  a  given  height  in  two  furnaces  of  different  construc- 
tion, and  in  which  different  materials  are  used.  Actual  experi- 
ments on  furnaces  carried  on  by  hot  blast  and  charcoal  have  fur- 
nished the  following  results  : — 

Directly  above  the  tuyere.      Nitrogen.     Carbonic  acid.      Carbonic  oxide.     Hydrogen. 

8   feet  63.07  "  35.01  1.92 

13     «  59.14  8.86  28.18  3.82 

22J   «  57.80  13.96  22.24  6.00 

25J   "  57.79  12.88  23.51  5.82 


Nitrogen. 

64.58 

Carb.  acid. 

5.97 

Carb.  oxide. 

26.51 

Hydrogen. 

1.06 

Carburetted 
hydrogen. 

1.88 

63.89 

3.60 

29.21 

2.07 

1.07 

62.34 

8.77 

24.20 

1.33 

3.36 

Nitrogen. 

Carbonic  acid. 

Carbonic  oxide. 

Hydrogen. 

61.07 

0.68 

36.84 

1.41 

64.66 

0.57 

33.39 

1.38 

63.59 

2.77 

31.83 

1.81 

60.70 

11.58 

25.24 

2.48 

REVIVING    OF  IRON.  209 

We  find  here,  what  might  have  been  expected,  a  gradual  in- 
crease of  the  carbonic  acid.  This  is  generated  by  the  contact  of 
carbonic  oxide  with  the  ore.  The  relative  amount  of  the  different 
gases  is  not  equal  in  different  furnaces,  for,  in  another  case,  the 
gases  were  mixed  in  the  following  proportions: — 

Directly  above 
the  tuyere. 

5}  feet 
11}   " 
17}   " 

The  gases  of  a  coke  furnace  exhibited  the  following  composi- 
tion:— 

Directly  above  the  tuyere. 

2  feet 
17J  " 
28    " 
31    " 

There  are,  particularly  in  coke  furnaces,  gases  of  a  compound 
character ;  but  these  have  little  to  do  with  practical  results,  the  aim 
of  our  investigations. 

From  the  above,  it  is  apparent  that  the  carbonic  acid  gas  increases 
as  the  current  of  gas  ascends ;  and  that,  on  an  average,  one-third 
of  the  carbonic  oxide  has  been  converted  into  carbonic  acid  before 
escaping  at  the  top.  If  the  carbonic  oxide  is  the  only  reagent  in 
the  conversion  of  ore  into  iron,  we  may  conclude  that  one-third  of 
the  fuel  has  been  properly  applied  for  the  purpose  for  which  it  was 
designed.  We  here  have  evidence  that  all  the  fuel  has  not  done  its 
duty;  otherwise,  all  the  carbonic  oxide  would  have  been  converted 
into  carbonic  acid,  and  all  the  hydrogen  into  water.  But  such  is 
not  the  case.  If  a  furnace  works  well,  there  will  be  more  carbonic 
acid  at  the  top  of  the  charges  than  there  will  be  if  a  furnace  works 
badly;  this  circumstance  accounts  for  the  different  appearance  of 
the  trunnel  head  flame. 

d.  The  theory  of  the  reduction  of  ore  will  then  be  simply  this : 
the  gases  ascending  in  the  furnace  leave  a  part  of  their  positive 
elements  to  combine  with  the  oxygen  of  the  ore,  that  is,  carbonic 
oxide  leaves  carbon,  and,  under  peculiar  circumstances,  hydrogen 
may  be  retained.  If  carbonic  oxide  absorbs  oxygen  from  the  ore, 
it  leaves  of  course  metallic  iron  or  protoxide,  and  the  ore,  in  de- 
scending, will  be  a  mixture  of  metallic  iron  and  foreign  matter.  If 
14 


210  MANUFACTURE   OF  IRON". 

that  process  is  not  well  performed,  some  oxides  of  iron  will  be  left 
in  the  mixture.  If  an  ore,  to  this  extent  prepared,  but  without 
any  surplus  of  carbon,  descends  into  the  hearth,  it  cannot  produce 
anything  but  white  iron;  for,  if  the  iron  is  once  heated  to  redness, 
and  melts,  it  absorbs  no  more  carbon.  All  the  carbon  required  for 
making  gray  iron  must  be  in  the  ore  before  it  sinks  into  the  hearth. 
For  this  and  many  other  reasons,  we  are  forced  to  assume  a  surplus 
of  free  carbon  in  the  gas  mixtures  of  the  blast  furnace — carbon,  if 
not  chemically,  at  least  mechanically,  mixed  with  the  gases,  and  so 
finely  diifused,  that  it  can  penetrate  into  the  pores  of  the  ore.  If 
we  adopt  this  theory,  that  is,  the  presence  of  free  carbon,  we  can 
account  for  many  apparent  irregularities  in  furnace  operations  for 
which  we  cannot  account  on  the  simple  assumption  that  the  gases 
ascend  in  their  constitutional  form.  By  adopting  this  theory,  we 
account  for  a  circumstance  otherwise  incomprehensible,  that  is,  the 
great  influence  exerted  by  the  pressure  of  the  blast ;  for  if  nothing 
else  than  carbonic  oxide  is  needed,  almost  any  pressure,  even  the 
weakest  blast,  will  accomplish  all  that  is  desired.  But  we  know, 
by  experience,  that  the  strongest  blast  which  a  given  kind  of  fuel 
will  bear  advantageously,  is  the  most  profitable.  It  appears,  from 
this,  that  the  blast  works  mechanically  as  well  as  chemically,  in  the 
destruction  of  coal;  and  that  a  certain  power  will  produce  particles 
of  coal  of  a  size  best  calculated  to  penetrate  the  pores  of  the  ore. 
If  these  particles  are  too  large,  they  cannot  reach  the  interior  of  the 
ore,  and  the  iron  will  be  white.  This  may  be  assigned  as  the  reason 
why  a  particular  pressure  of  the  blast  is  required  to  produce  gray 
metal.  If  the  blast  is  too  weak,  it  produces  white  iron  from  defi- 
ciency of  carbon  in  the  ore ;  and  if  too  strong,  the  consequences  are 
equally  injurious.  Such  an  admixture  of  free  carbon  will  be,  of 
course,  uniformly  diffused  among  the  gases,  and  penetrate  the 
porous  ores  more  readily  than  even  the  gases  themselves,  on  ac- 
count of  the  superior  affinity  of  carbon  for  oxygen. 

A  further  evidence  of  the  agency  of  free  carbon,  in  the  smelting  of 
gray  iron,  is  in  the  fact  that  compact,  close  ores,  of  whatever  chemical 
composition,  will  not  produce  gray  iron.  Should  an  atmosphere  of 
carbonic  oxide,  or  even  carbon  in  any  other  form,  alone  be  needed  to 
smelt  gray  metal,  there  would  be  no  difficulty  in  manufacturing  gray 
iron  from  any  kind  of  ore.  But  this  is  not  the  case.  From  com- 
pact specular  ore,  magnetic  ore,  the  carbonates,  and  ores  too  hard 
burnt,  we  cannot  make  gray  iron,  whatever  amount  of  coal  we  em- 
ploy, and  whatever  kind  of  blast  we  use.  A  certain  aggregate 


REVIVING   OF   IRON.  211 

form  of  the  ore  is,  under  all  conditions,  required  for  the  manufac- 
ture of  gray  metal ;  and  this  is  an  open,  porous  form.  We  find 
that  pieces  of  ore  taken  from  the  furnace  when  in  good  condition 
are,  towards  the  boshes,  of  a  black,  and,  higher  up,  of  a  brown  color. 
An  analysis  of  such  ores  has  never  been  made ;  such  an  analysis 
would,  of  course,  be  attended  with  great  difficulties  ;  but  if  the 
composition  of  the  ores,  in  their  gradual  descent  from  the  top  to 
the  bottom,  were  fairly  tested,  a  great  accession  to  our  knowledge 
would  be  realized. 

e.  The  operation  in  a  furnace  is,  then,  as  follows :  In  the  upper 
part  of  the  stack,  the  water  of  the  materials  is  expelled,  hydrogen 
from  the  coal  is  driven  off,  and  the  porous  ore  is,  to  a  greater  or  less 
degree,  saturated  with  carbon,  by  means  of  which  the  carbonic  oxide 
serves  to  reduce  a  part  of  the  ore  to  protoxide.  The  ore,  in  this 
condition,  will  appear,  before  entering  the  hearth,  like  a  brick  winch 
has  been  exposed  to  the  interior  heat  of  a  charcoal  kiln  or  a  coke 
oven — a  mixture  of  iron  ore,  foreign  matter,  and  carbon.  This 
applies  to  cases  in  which  the  furnace  operations  are  in  good  order, 
and  in  which  gray  iron  is  manufactured.  All  circumstances  which 
interfere  with  the  regular  course  of  this  work  contravene  favor- 
able results,  particularly  in  relation  to  the  quality  of  the  metal. 

/.  The  conditions  under  which  such  a  state  of  things  may  be  ex- 
pected, are,  a  porous  and  dry  ore,  a  blast  neither  too  weak  nor  too 
strong,  and  a  low  temperature  in  the  upper  parts  of  the  stack.  A 
high  temperature  is  not  sufficient  to  produce  a  combination  of  iron 
and  carbon,  at  least  when  the  iron  is  once  in  a  liquid  state.  On 
the  other  hand,  if  the  metal  is  liquid,  it  is  difficult  to  separate  car- 
bon from  it.  Where  the  upper  part  of  the  stack  is  too  warm, 
the  hydrogen  liberated  from  the  coal  will  combine  with  the  oxygen 
of  the  ore,  and  leave  metallic  white  iron  in  the  ore.  This  iron  has 
no  affinity  for  carbon,  and  will  sink  into  the  hearth  without  it. 
This  also  happens  where  the  highest  part  of  the  furnace  is  too  warm, 
so  that,  in  the  limited  space  through  which  the  materials  pass,  the 
ore  is  sufficiently  heated,  without  a  protecting  coat  of  carbon;  and 
also  where  the  coal  contains  too  much  hydrogen,  as  in  the  case  of 
•half  charred  wood,  bad  coke,  or  bituminous  coal.  If  too  much 
hydrogen  is  present,  it  is  not  entirely  expelled  until  the  materials 
are  very  low  in  the  stack  ;  but  then  it  has  sufficient  time,  on  its  way 
to  the  top,  to  combine  with  some  of  the  oxygen  of  the  ore,  even  with 
the  oxygen  of  the  silex,  or  other  oxides.  We  invariably  find  that 
the  iron  made  under  such  circumstances  is  bad ;  for,  where  hydro- 


212  MANUFACTURE    OF   IRON. 

gen  exerts  any  action  upon  ore,  it  deprives  it  of  its  oxygen,  and 
thus  destroys  that  affinity  for  carbon  necessary  to  make  gray  metal. 
If  the  hydrogen  is  permitted  to  exert  a  greater  degree  of  influence, 
it  will  decompose  silex,  lime,  and  manganese,  which  will  combine 
as  an  alloy  with  the  iron,  and  injure  its  strength  and  ductility.  The 
best  means  of  obviating  this  influence  of  the  hydrogen — at  least,  the 
best  method  of  making  it  as  little  dangerous  as  possible — is  to  em- 
ploy low  stacks,  wide  throats,  and  an  abundance  of  strong  blast;  or, 
if  foundry  metal  is  to  be  made,  hot  blast.  Narrow  tops  and  weak 
blast  will  not  answer  for  bituminous  fuel.  We  may  expect  to  find 
bitumen  or  hydrogen  in  imperfectly  charred  wood,  in  soft,  half  burnt 
coke,  or  in  anthracite  of  bituminous  character.  Under  all  these 
circumstances,  we  can  most  effectually  work  with  a  wide  trunnel 
head,  even  though  the  other  conditions  cannot  be  complied  with. 
A  narrow  throat  will  expose  the  ore,  in  its  almost  raw  state,  to  the 
influence  of  the  hydrogen  ;  and  in  that  condition,  without  any  car- 
bon to  protect  the  ore,  the  mischief  is  consummated  before  the  ore 
is  fairly  in  the  furnace.  We  will  endeavor  to  make  this  subject 
clearly  understood.  Fig.  TO  represents  a  furnace  with  a  narrow 
top,  examples  of  which  we  have  frequently  seen.  The  arrows  in- 
dicate the  current  of  the  gases.  We  may  here  very  easily  perceive 
that  the  heat  and  action  of  the  gases  on  the  ore  are  to  a  great  degree 
lost;  for  it  is  evident  that  the  coal  will  be  pressed  towards  the 
lining,  and  that  the  heavier  ore  will  remain  in  the  centre.  It  is 
reasonable  to  suppose  that  the  gases,  instead  of  winding  them- 
selves through  the  close,  heavy  ore,  will  choose  the  easier  passage 
through  the  coal.  Their  action  upon  the  ore  is  confined  to  the 
short,  narrow  passage  in  the  throat.  Narrow  tops,  weak  blast,  and 
high  stacks  may  answer  for  good,  coarse  fuel,  and  for  open,  porous 
ores,  which  are  not  loamy;  but,  in  all  other  cases,  they  answer  im- 
perfectly. Where  well-burnt  or  open  ores,  and  dry  and  well-charred 
fuel,  are  available,  it  is  advisable  to  have  wide  throats,  strong  blast, 
and  stacks  that  are  not  too  high.  In  cases  in  which  the  best  mate- 
rials are  not  at  our  service,  or  in  which  they  are  too  expensive, 
we  should  use  all  the  means  to  arrive  at  favorable  results  which 
circumstances  may  afford  us. 

g.  The  above  principles  are  not  deduced  from  theory  :  the  facts 
on  which  they  are  based  were  observed  prior  to  the  existence  of 
the  science  of  the  blast  furnace,  as  the  following  considerations 
•will  establish  : — 


REVIVING   OF  IRON.  213 

We  find  that,  in  Sweden,  where  magnetic  ores  are  smelted,  as 
well  as  in  Russia,  and  at  the  furnace  at  Cold  Springs,  N.  Y.,  wide 
trunnel  heads  are  employed.  We  allude  only  to  those  establishments 
in  which  the  business  is  in  so  high  a  state  of  cultivation  as  to  pro- 
voke imitation.  At  these  places,  we  find  not  only  the  manufacture 
of  a  superior  metal,  but  a  remarkable  reduction  in  the  consump- 
tion of  fuel.  In  Styria,  Western  Germany,  and  at  some  establish- 
ments in  France,  the  very  difficult  sparry  carbonates  are  princi- 
pally smelted.  These  carbonates  are  never  perfectly  oxidized. 
Wide  tops  are  employed  at  these  places,  which  are  celebrated  on 
account  of  the  small  amount  of  fuel  consumed.  In  our  own  country, 
scarcely  any  of  these  refractory  ores  are  smelted ;  and  at  a  few 
furnaces  in  New  Jersey,  New  York,  and  the  Eastern  States,  where 
they  are  used,  mixtures  are,  to  a  greater  or  less  extent,  worked ; 
and  the  ore  charges  are  brought  to  a  medium  proportion  of  the 
magnetic  and  peroxide  ores.  We  find  an  exception  to  this  at  Lake 
Champlain ;  but  of  this  locality,  we  shall  speak  hereafter.  If  we 
apply  the  above  principles  to  the  fuel,  we  find  that  some  Russian 
furnaces,  employing  raw  wood,  make  use  of  very  wide  tops,  even  from 
five  to  six  feet  square,  and  work  with  very  strong  blast,  generally 
with  but  one  tuyere,  and  with  the  exclusion  of  hot  blast.  Some  French 
and  German  furnaces,  which  employ  either  red  coal  or  kiln-dried 
wood  successfully,  have  been  compelled  to  make  use  of  wide  tops 
and  strong  blast.  Of  the  extent  to  which  experiments  with  wood 
in  furnaces  have  succeeded  in  the  United  States,  we  have  no  satis- 
factory information :  but  we  are  inclined  to  believe  that,  in  an 
economical  point  of  view,  such  experiments  would  fail ;  for  there 
are  few  localities  where  both  ore  and  fuel  are  found  in  proper  con- 
dition. Economically,  open,  porous  oxides  work  better  with  charcoal 
than  with  wood.  Refractory  rich  ores  can  be  smelted  with  wood. 

Anthracite  furnaces  require  wider  tops  than  coke  furnaces ;  while 
the  latter  require  far  wider  tops  than  charcoal  furnaces.  This  width 
of  the  top  may  be  considered  the  most  essential  improvement  on 
the  blast  furnace  which  is  supplied  by  anthracite  coal.  The  height 
of  the  stack  in  anthracite  is  much  less  than  in  coke  furnaces  ;  and 
somewhat  lower  than  in  charcoal  furnaces.  Anthracite  furnaces 
vary  from  thirty  to  thirty-five  feet  in  height;  charcoal  furnaces  from 
thirty  to  forty  feet ;  and  coke  furnaces  from  forty  to  sixty  feet.  The 
width  of  the  trunnel  head  varies,  in  the  United  States,  considerably. 
In  Pennsylvania,  Ohio,  Kentucky,  and  Tennessee,  the  width  of  fur- 
naces at  the  boshes  is  nine,  and  often  ten  feet,  and  at  the  top  from 


214  MANUFACTURE    OF  IRON. 

eighteen  to  twenty  inches ;  or,  in  the  proportion  of  thirty  square 
feet  at  the  boshes  to  one  square  foot  at  the  top.  The  Cold  Spring 
furnace  measures  at  the  boshes  nine  feet,  and  at  the  top  thirty-two 
inches.  Here  the  proportion  is  eleven  feet  at  the  boshes  to  one  foot 
at  the  top.  The  dimensions  of  charcoal  furnaces,  in  Europe,  which 
smelt  refractory  ores,  are  generally  in  the  proportion  of  five  feet 
at  the  boshes  to  one  foot  at  the  throat ;  frequently  in  the  propor- 
tion of  four  to  one.  In  coke  furnaces,  the  proportion  of  the  hori- 
zontal section  of  the  boshes  to  that  of  the  top  is  seldom  less  than 
four  to  one,  though  sometimes  even  2.5  to  1. 

In  anthracite  furnaces,  the  diameter  of  the  throat  is  six  feet, 
and  that  of  the  boshes  twelve  feet ;  that  is,  in  the  proportion  of 
one  to  four.  But  sometimes  the  boshes  measure  thirteen,  and  the 
tops  eight  feet  square  ;  in  this  case,  we  have  the  proportion  of  two 
to  one.  When  we  take  into  consideration  the  small  height  of  the 
stack,  and  the  strong  blast  which  is  applied,  we  shall  find  that  this 
arrangement  in  anthracite  furnaces  is,  in  an  economical  point  of 
view,  very  favorable ;  for,  instead  of  retarding,  it  facilitates  the 
vent  of  the  gases.  Narrow  tops  answer  where  loamy  ore  and  soft 
coal  are  used  ;  but  in  such  cases,  if  we  expect  favorable  results,  we 
should  employ  weak  blast  and  high  stacks.  But  these  conditions 
can  be  observed  only  where  coal  and  labor  are  cheap.  If  we  are 
in  doubt  concerning  the  proper  dimensions  of  a  furnace,  our  best 
course  is  to  commence  with  a  comparatively  low  stack,  wide  throat, 
and  with  as  high  a  pressure  in  the  blast  as  the  fuel  will  possibly 
bear. 

h.  The  foregoing  demonstrations  are  designed  to  suggest  the 
method  of  producing  an  excellent  quality  of  metal.  It  is  evident 
that  the  ore  should  be  so  prepared  in  the  upper  part  of  the  furnace 
that  it  may  be  brought  into  the  crucible  in  the  best  possible  con- 
dition for  producing  the  best  metal  which  circumstances  will  per- 
mit ;  for  we  cannot  expect  to  make  gray  iron  from  raw  magnetic 
ore,  from  clinkers  of  ore  burnt  too  hard,  or  from  forge  cinders. 
But  though  we  are  unable  to  smelt  gray  iron  of  good  quality  from 
these  materials,  nothing  should  prevent  us  from  endeavoring  to 
make  the  best  use  of  the  stock  at  our  disposal.  If,  by  means 
of  scientific  knowledge  and  industry,  we  obtain  a  cheaper  stock, 
or  one  of  better  quality,  we  should  not  refuse  useful  material,  sim- 
ply because  our  furnace  is  not  prepared  to  receive  it. 

i.  If  one  of  the  conditions  of  success,  in  blast  furnace  opera- 
tions, is  that  the  ore  should  be  properly  prepared,  that  is,  saturated 


REVIVING   OF   IRON.  215 

with  carbon  before  it  reaches  the  hearth,  or  arrives  at  the  melting 
heat  of  iron,  it  is,  of  course,  a  question  of  great  importance,  what 
kind  of  ore,  and  what  composition,  are  best  adapted  to  receive 
the  carbon,  and  to  retain  it.  It  is  easily  understood  that  compact 
ores,  that  is,  ores  of  great  specific  gravity,  even  if  they  are  per- 
oxides, and  unburnt  magnetic  ores,  spathic  or  argillaceous  car- 
bonates, are  not  well  calculated  to  absorb  carbon.  Silicates  or  alu- 
minatcs  should  not  be  smelted,  for  these  ores  are  so  compact  that 
no  carbon  can  penetrate  them.  The  question  is  not  so  much  one 
of  chemical  composition,  as  of  mechanical  or  aggregate  form  of  the 
ore.  Such  a  form  is  the  most  easily  produced  in  the  peroxide;  for, 
under  most  conditions,  this  oxide,  if  rubbed,  yields  an  impalpable 
powder ;  even  when  in  compact  masses,  its  powder  is,  of  all  others, 
the  finest.  For  this  reason,  and  for  no  other  reason,  we  roast  the 
ore.  We  roast  the  magnetic  ore  to  open  crevices ;  roast  the  car- 
bonates to  expel  the  carbonic  acid  gas,  and  open  the  pores  ;  and 
burn  hydrates  to  evaporate  the  water  belonging  to  their  chemical 
composition,  and  thus  make  room  for  carbon.  We  endeavor,  in 
roasting,  to  raise  the  oxidation  of  the  ore  to  a  peroxide  ;  with  the 
specific  object  of  increasing  the  affinity  of  the  ore  for  carbon,  or 
carbonic  oxide.  If  the  ore  absorbs  more  carbonic  oxide  in  one 
instance  than  in  another,  and  if  the  composition  of  the  gas,  that  is, 
carbonic  oxide  and  free  carbon,  is  the  same  in  both  cases,  then  the 
greater  the  amount  of  oxygen  it  contains,  the  greater  will  be  the 
amount  of  carbon  which  will  condense  upon  and  penetrate  the  ore. 
For  these  reasons,  roasted  and  oxidized  ores  are  required  in  the 
manufacture  of  gray  iron.  This  theory  is  in  perfect  harmony 
with  experience;  and  a  practical  iron  manufacturer  will  find  no 
difficulty  in  arriving  at  evidence  from  facts  within  his  knowledge. 
Jc.  Ores  are,  in  most  cases,  not  only  composed  of  iron  and  oxygen, 
but  are  a  compound  of  oxide  of  iron  and  more  or  less  foreign  mat- 
ter. The  mixtures  of  oxides  of  iron  and  foreign  matter  are  innu- 
merable ;  still,  where  this  mixture  takes  place  beyond  a  given  de- 
gree, the  compound  ceases  to  constitute  an  iron  ore.  But  the 
quality  rather  than  the  quantity  of  foreign  matter  in  the  ore  de- 
termines this  question,  as  we  shall  presently  see.  Nevertheless,  a 
mineral  which  contains  less  than  twenty  per  cent,  of  iron  is  not 
usually  considered  an  ore  of  iron.  Silex,  lime,  and  clay  are  the 
common  admixtures.  Other  ingredients,  such  as  magnesia,  man- 
ganese, and  titanium,  whatever  influence  they  may  have  in  par- 
ticular cases,  may,  in  ordinary  investigations,  be  neglected. 


211S  MANUFACTURE   OF  IRON. 

I.  The  next  important  question  is,  what  influence  will  any  mix- 
ture of  foreign  matter  have  upon  the  iron  ore,  so  far  as  the  absorp- 
tion of  carbon  is  concerned  ?  To  answer  this  we  would  simply  say, 
that,  according  to  science,  and  experiments  in  the  laboratory,  clay 
possesses  the  greatest  affinity  for  carbon ;  next  in  order  is  silex  ; 
and  then  lime.  This  classification,  however  perfectly  true  in  theory, 
is  not  confirmed  by  practical  results.  In  this  case,  theory  and  prac- 
tice appear  to  be  at  variance  with  each  other ;  but  when  we  take 
into  consideration  that  the  mechanical  form  of  the  matter  is  the 
cause  of  this  difference  in  the  results  arrived  at  by  theory  and 
practice,  this  apparent  exception  to  a  general  rule  of  chemistry  is 
explained.  Iron  manufacturers  generally  consider  calcareous  ore 
the  most  favorable  of  all  ores  for  the  manufacture  of  gray  or  foundry 
metal.  Clay  ore,  and  then  silicious  ore,  come  next  in  importance. 
But  we  should  be  cautious  how  far  we  base  practical  results  upon 
this  experience,  for  it  frequently  happens  that  the  theory  which 
we  have  deduced  from  practice  fails  ;  and  from  this  failure  great 
losses  ensue.  The  above  practical  rule  is  applicable  only  where 
the  lime  or  calcareous  ores  are,  as  is  generally  the  case,  already 
mixed  with  foreign  matter,  and  where  silicious  and  argillaceous 
ores  are  in  their  purity.  Experiments,  practically  confirmed,  made 
by  Mushet,  and  related  in  his  papers  on  iron  and  steel,  clearly 
prove  that  clay  has  the  greatest  affinity  for  carbon ;  next  to  clay 
comes  silex,  and  then  lime.  A  low  temperature  and  very  little  fuel 
will  revive  iron  from  a  mixture  of  clay  and  oxide  of  iron  ;  but  all 
the  iron  the  mixture  contains  will  not  be  revived,  because  clay  is 
infusible  by  itself,  and  retains  some  particles  of  iron,  and  of  course 
carbon.  The  iron  is  retained  as  an  element,  or  radical,  of  an  alkali. 
A  stronger  alkali  is  necessary,  by  combining  with  the  clay,  to  thrust 
the  iron  from  its  hiding-place.  This  affinity  of  the  carbon  and 
iron  for  the  clay  might  be  dissolved,  if  the  aggregate  form  of  the 
clay  would  permit  the  formation  of  larger  globules  of  iron ;  for 
these,  following  the  law  of  gravitation,  would  separate  in  spite  of 
affinity.  Nearly  the  same  thing  happens  with  a  mixture  of  silex 
and  oxide  of  iron,  with  this  difference,  that  silex  does  not  absorb 
carbon  so  readily  as  clay,  and  does  not  revive  iron  by  so  low  a 
temperature,  and  with  so  little  fuel.  But  if  no  alkali  combines,  at 
the  proper  time,  with  the  clay  or  silex,  neither  would  yield  all  its 
iron,  even  though  revived  and  carbonized.  Of  these  earths,  lime 
is  the  very  last  which  absorbs  carbon  and  revives  iron ;  but  then  it 
precipitates  all  its  iron  at  once,  because  carbonate  of  lime  is  fusible 


REVIVING   OF  IRON.  217 

by  itself,  and  will,  when  concentrated  into  a  melted  slag,  squeeze 
the  iron  out. 

m.  Agreeably  to  these  principles,  clay  ores  will  require  a  low 
temperature  in  the  upper  part  of  the  stack.  We  should  endeavor 
to  extend  this  temperature  to  as  low  a  depth  as  possible.  This  will 
prevent  the  precipitation  of  iron  before  any  lime  is  sufficiently  heated 
to  receive  the  clay,  and  will  consequently  prevent  the  combination 
of  iron  and  clay  into  an  aluminate,  from  which  it  is  difficult  to  sepa- 
rate the  iron.  Silex  or  silicious  ore  is  very  nearly  of  the  same 
character,  but  will  permit  of  a  higher  degree  of  heat,  without  much 
danger.  With  calcareous  ore  we  may  raise  the  heat  as  high  in  the 
stack  as  we  please,  without  endangering  the  result.  These  prin- 
ciples, deduced  from  theory,  coincide  exactly  with  experience  at  the 
furnace.  If  we  smelt  pure  calcareous  ore — not  what  is  commonly 
called  the  limestone  ore,  for  this  is  generally  a  precipitate  of  iron 
upon  a  limestone  bed,  and  contains  very  little  lime — we  need  a 
strong  heat  in  the  furnace,  and  an  abundance  of  fuel.  The  reason 
of  this  is  that  the  upper  heat  of  the  stack  and  the  action  of  the  re- 
viving gases  are  entirely  lost,  for  lime  and  limestone  ore  condense 
little  or  no  carbon.  We  thus  find  that  pure  calcareous  ores  are  not 
the  most  profitable;  and  we  shall  make  a  better  use  of  the  fuel,  if 
along  with  it  we  mix  silicious  and  clay  ore.  In  this  way,  we  shall 
not  only  derive  greater  profit  from  the  gases,  but  a  lower  tempera- 
ture of  the  stack  will  enable  us  to  secure  many  advantages.  Fo- 
reign admixtures  are  thus  shown  to  be  unaccompanied  with  injurious 
results;  but  this  principle  cannot  be  extended  to  a  chemical  admix- 
ture or  combination.  Chemical  compositions  of  silex,  clay,  and 
lime  are  of  very  difficult  decomposition;  the  very  fact  that  their 
texture  is  so  close,  is  the  reason  why  no  carbon  can  penetrate  and 
combine  with  the  oxygen  of  the  iron.  This  is  applicable  also  to 
forge  and  puddling  cinder,  and  to  clinkers,  and  to  ore  very  hardly 
burnt. 

n.  From  these  statements,  it  is  evident  that  a  proper  mixture 
of  different  ores  will  be  beneficial,  so  far  as  the  use  of  fuel  is  con- 
cerned; and  that  the  more  closely  and  intimately  the  ores  are  mixed, 
the  better  will  be  the  result.  A  medium  temperature  is  a  security 
that  the  furnace  will  work  well,  and  guarantees  economy  of  fuel  and 
a  favorable  product.  Where  proper  mixtures  of  foreign  matter  are 
already  contained  in  the  ore,  the  most  profitable  work  may  of  course 
be  expected.  Ores  of  this  kind  are  frequently  met  with  in  the  coal 
formations,  as  precipitates  upon  limestone  or  clay.  This  is  the  case 


218  MANUFACTURE   OF  IRON. 

at  Huntingdon  county,  Pa.,  and  at  other  places.  The  out-crop  ores 
of  the  anthracite  coal  series,  as  well  as  the  Western  coal  fields,  ex- 
hibit generally  this  composition.  A  great  majority  of  the  Western 
furnaces,  such  as  those  at  Hanging  Rocfk,  and  at  many  places  along 
the  Alleghany  River,  work  these  ores. 

We  have,  we  think,  sufficiently  proved  that  the  aggregate  form — 
the  mechanical  composition — of  an  ore  has  an  important  hearing 
upon  the  operations  of  a  furnace ;  but  it  is  obvious  that  the  chemical 
relations  must  be  still  more  important.  To  arrive,  by  the  surest 
and  shortest  method,  at  a  clear  and  comprehensive  conclusion,  we 
shall  describe  the  particular  behavior  of  each  kind  of  ore. 

o.  If  we  charge  a  furnace  with  unroasted  magnetic  ore,  the  ore 
will  sink  with  the  coal  charges  unaltered  until  it  arrives  at  a  cer- 
tain point,  when  it  will  melt  into  a  more  or  less  liquid  slag.  This 
slag  will  pass  through  a  column  of  hot  coal,  when  a  portion  of  the 
iron  will  be  revived;  another  portion  will  combine  with  silicious 
and  aluminous  matter,  and  form  cinder,  which  is  lost.  The  iron 
which  results  is  not  gray.  The  carbonates,  and  other  compact  and 
heavy  ores,  exhibit  the  same  peculiarities.  If  limestone  is  charged 
along  with  the  ore,  a  large  quantity  of  iron  will  be  revived ;  still, 
a  great  deal  of  iron  is  lost.  In  no  case  should  we  expect  gray 
iron;  for,  though  it  should  happen  that  some  carburetted  iron  has 
been  formed  in  the  furnace  about  the  hearth,  yet  so  long  as  the 
cinder  contains  protoxide  of  iron,  the  carbon  from  the  gray  iron  in 
the  hearth  will  be  absorbed,  and  iron  from  the  cinder  revived.  The 
latter  is  the  case  when  the  ores  contain  foreign  matter ;  but,  if  the 
ores  contain  little  or  no  foreign  matter,  there  will  not  be  sufficient 
cinder  even  to  protect  the  iron  from  the  influence  of  the  oxygen  of 
the  blast.  In  this  case,  the  iron  must  of  course  be  white.  The 
ores  may  be  compact  or  porous.  The  result  is,  in  both  cases,  the 
same;  for,  if  carburetted  iron  is  formed  in  the  upper  parts  of  the 
furnace,  without  a  protecting  cinder,  it  will  be  white  before  it  ar- 
rives in  the  crucible.  Satisfactory  results  cannot  be  obtained  from 
these  ores,  unless  we  have  a  warm  furnace,  and  unless  the  heat  is 
raised  to  a  considerable  height  in  the  stack. 

p.  If  an  iron  ore  contains  foreign  matter,  and  if  this  matter  is  a 
single  earth,  in  itself  refractory,  the  mechanical  form  of  the  ore  may 
be  the  most  advantageous  ;  but  the  metal  which  results  will  always 
be  white.  When  a  furnace  is  charged  with  clay  ore,  the  ore  will, 
in  its  descent,  absorb  and  condense  carbon.  When  the  carburetted 
metal  arrives  within  reach  of  the  blast,  the  carbon  will  be  absorbed 


REVIVING   OF   IRON.  219 

by  the  carbonic  acid,  and  the  iron  will  arrive  whitened  in  the  cru- 
cible ;  the  remaining  iron  yet  in  the  clay  will  be  highly  carburetted  ; 
but  the  clay  cannot  melt  and  protect  the  iron.  The  result  is  white 
iron;  and,  if  no  limestone  is  present,  an  aluminate  of  iron,  as  cinder. 
What  we  have  stated  is  applicable,  in  most  respects,  to  silicious 
ore ;  also  to  calcareous  ore,  with  this  difference,  that,  in  the  latter 
case,  no  protoxide  of  iron  is  needed  to  flux  the  cinder.  If,  by  ap- 
plying an  excess  of  fuel,  we  try  to  revive  all  the  iron  from  the  ore, 
or,  at  least,  to  revive  it  in  greater  quantity,  then,  with  clay  as  well 
as  silicious  ore,  we  receive  a  tenacious  cinder  in  the  hearth  below 
the  tuyere,  which  retains  the  globules  of  iron  on  its  surface.  If  a 
dark  gray  carburet  comes  down,  it  will  soon  become  white  iron 
within  the  influence  of  the  blast.  Should  the  cinder  not  be  suffi- 
ciently liquid  to  permit  the  iron  to  pass  through  it,  the  iron  will 
oxidize,  and  form  protoxide  to  the  cinder,  until  it  effects  a  passage. 
The  necessity  of  fluxes  is  thus  clearly  seen. 

q.  If  we  charge  a  furnace  with  poor  ore,  with  an  admixture  of  a 
refractory  character,  in  a  state  of  fine,  impalpable  aggregation,  as 
is  generally  the  case  with  clay  ores,  and  particularly  the  case  with 
some  silicious  ores,  the  iron  will  be  revived  by  a  comparatively  low 
temperature,  and  for  this  reason  will  combine  with  a  large  amount  of 
carbon.  But  this  carbon  cannot  be  retained,  if  the  original  globules 
of  iron  are  exposed  to  the  direct  influence  of  the  blast ;  for  these 
grains  of  melted  metal  are  so  small  that  they  can  pass  through  only 
a  very  liquid  cinder.  Should  the  cinder  not  be  sufficiently  liquid, 
the  resulting  metal  will  be  white.  This  is  another  reason  why  the 
smelting  of  gray  iron  from  clay  and  some  silicious  ores  is  so  difficult. 
To  arrive  at  desirable  results,  it  is  advisable  to  have  fine  clay  ore 
along  with  silicious  ore.  This  ore  revives  a  portion  of  its  iron  by  a 
low  heat,  and  is,  of  course,  highly  carburetted.  If  the  iron  produced 
descends,  and  finds,  on  its  way,  silicious  ore  ready  to  deliver  iron, 
it  will  combine  with  it,  and  form  a  larger  mass.  If  this  combination, 
in  its  further  descent,  comes  in  contact  with  a  calcareous  ore,  which, 
under  ordinary  circumstances,  would  not  liberate  iron,  the  carbu- 
retted iron  of  the  clay  and  silicious  ore  will  draw  with  it  a  portion 
of  iron  from  the  calcareous  ore ;  this  augmented  combination  will 
resist  the  influence  of  the  blast,  and  by  its  ponderability  will 
work,  with  greater  readiness,  a  passage  through  the  melted  cinder 
below  the  tuyere.  The  remaining  iron  in  the  clay  ore,  which,  in 
most  pases,  amounts  to  half  the  original  quantity,  will  be  enclosed 


220  MANUFACTURE    OF   IRON. 

in  the  unaltered  piece  of  ore  until  it  arrives  in  the  hearth  below 
the  tuyere.  If,  at  that  point,  it  meets  with  silicious  or  calcareous 
ore,  both  of  which  are  in  the  same  condition,  the  different  earths, 
being  in  a  high  temperature,  will  combine,  form  a  liquid  cinder, 
and  squeeze  the  iron  out.  The  iron,  having  been  protected  from 
the  blast  by  the  refractory  cinder  which  surrounds  it,  is  now  per- 
fectly protected  against  the  blast  by  the  melting  cinder,  composed 
of  the  foreign  matter  of  the  different  ores. 

The  case  which  we  have  described  seldom  happens,  for  there  are 
few  clay  ores  which  do  not  contain  a  portion  of  silex  ;  few  silicious 
ores  which  contain  no  lime,  or  magnesia,  or  clay  ;  and  scarcely  any 
calcareous  ore  which  does  not  contain  a  portion  of  clay  or  silex. 
The  above  is  a  theoretical  case,  brought  forward  merely  to  illus- 
trate a  principle.  There  is  a  possibility  that  similar  coincidences 
may  exist  in  practice ;  but  they  can  happen  only  very  seldom. 

r.  Experience  has  clearly  proved  that,  of  all  ores,  those  which 
flux  themselves  are  the  most  profitable.  That  is  to  say,  any  mix- 
ture of  ore,  or  any  individual  ore,  which  produces  good  metal, 
and  a  liquid  cinder  free  of  iron,  is  more  profitable  than  those  ores 
which  require  the  interference  of  art.  What  constitutes  a  good 
cinder,  we  shall  investigate  hereafter.  We  shall  confine  our  atten- 
tion at  present  simply  to  the  iron,  and  to  the  operations  which  take 
place  in  the  furnace.  If  clay  ore,  as  already  explained,  yields  a 
portion  of  its  iron  very  readily,  we  may  infer  that  this  is  grayer  than 
any  other  portion,  because  carbon  combines  more  easily  with  iron 
at  a  low  than  at  a  high  temperature :  but  this  carburetted  iron  is 
destroyed  on  account  of  the  refractory  quality  of  the  clay.  If 
the  clay,  mixed  with  the  ore,  should  contain  a  portion  of  lime  and 
silex,  its  refractory  character  would  be  diminished,  and  the  car- 
buretted iron  in  the  inside  of  the  fragment  of  ore  would  be  more 
perfectly  protected  against  the  influence  of  the  blast.  If  the  car- 
buretted iron  thus  protected,  should  find  an  alkali  in  the  cinder, 
below  the  tuyere,  waiting  to  receive  the  foreign  matter,  it  will 
descend  with  scarcely  any  loss  of  carbon.  From  this  it  is  evident 
that  we  may  expect  gray  metal  from  mixed  clay  ores,  if  lime  or 
any  alkali  is  present  in  the  hearth ;  but  not  otherwise.  If  the 
foreign  admixtures  of  the  ore  are  not  of  such  a  nature  as  to  form  a 
liquid  cinder,  the  cinder  must  be  made  sufficiently  liquid  by  the 
addition  of  flux,  or  by  the  loss  of  a  portion  of  iron. 

In  reality,  there  are  few  purely  clay,  silicious,  or  calcareous  ores. 


REVIVING   OF   IRON.  221 

The  native  deposits  are,  to  a  greater  or  less  extent,  compounds  of 
iron  ore,  and  of  various  foreign  matters;  still  the  clay  and  silicious 
ores  predominate.  Calcareous  ores  are  very  seldom  met  with  on 
this  continent.  Therefore,  in  most  cases  where  iron  is  smelted,  an 
admixture  of  limestone,  instead  of  calcareous  ore,  will  answer  every 
purpose.  A  mixture  of  lime  and  iron  is  always  available ;  for 
pure  lime  will  sink  into  the  hearth,  and  remain  in  lumps  until 
slowly  dissolved  by  descending  clay  or  silex.  If  lime  contains  a 
quantity  of  iron,  or  other  foreign  matter,  it  will  melt  above  the 
tuyere,  leave  the  hearth  free  of  any  obstruction  to  the  descending 
iron,  and  give  the  blast  free  play  at  the  coal;  therefore,  a  lime- 
stone which  is  not  refractory  is  preferable. 

s.  The  above  process  takes  place  when  silicious  and  clay  ores  are 
to  be  smelted,  and  when  the  flux  is  limestone.  But  let  us  consider 
the  case  in  which  calcareous  ore  is  to  be  smelted,  and  fluxed  with 
silex  or  clay.  As  mentioned  above,  calcareous  ores  require  a  strong 
heat,  and  permit  the  raising  of  the  heat  to  an  uncommon  height  in 
the  stack.  On  that  account,  more  fuel  is  consumed  for  these  than 
for  other  ores.  If  calcareous  ore  is  smelted  by  charcoal,  which 
contains  but  a  small  quantity  of  silex,  the  ore  will  melt  into  a  slag, 
as  in  the  case  of  the  magnetic  ore,  and  in  descending  will  lose 
some  of  its  iron.  If  the  heat  is  strong,  and  if  more  iron  is  separated, 
some  of  the  lime  will  either  be  blown  off  at  the  trunnel  head,  which 
we  often  observe  issuing  in  a  white,  fine  dust,  or  will  combine  with 
the  silex  of  the  coke  or  stone  coal,  and  descend  to  the  hearth.  Under 
all  circumstances,  a  part  of  the  lime  will  descend  below  the  tuyere, 
and  if  it  does  not  find  silex  or  clay  in  the  cinder,  it  will  attack  the 
hearthstones;  and  by  this  means  the  lime  is  saturated  with  clay  or 
silex,  becomes  liquid,  and  is  in  a  condition  fit  to  be  discharged.  In 
this  case,  the  iron  is  of  no  use  in  fluxing  the  limestone,  for,  at  the 
high  temperature  of  the  furnace  and  hearth,  all  the  iron  is  precipi- 
tated; and  if  there  is  no  carbonic  acid  in  the  lime,  or  if  no  clay  or 
silex  is  present,  no  combination  between  them  is  possible.  Calca- 
reous ores  should  be  fluxed  by  clay  or  silex.  Pure  sand  and  fire  clay 
cannot  be  of  any  service  ;  they  do  not  melt ;  they  sink  gradually 
into  the  hearth;  and  if  any  iron  from  the  calcareous  ore  is  liberated, 
it  has  a  tendency  to  combine  with  silex  or  clay.  The  first  chance 
of  receiving  oxygen  affords  an  opportunity  of  forming  protoxide  of 
iron,  and  silicates  or  aluminates  of  iron.  Such  disturbances  happen 
frequently  with  calcareous  ore.  An  excess  of  lime  in  the  ore  is,  to 


222  MANUFACTURE   OF  IRON. 

all  appearances,  not  sufficient  to  precipitate  the  whole  of  the  iron, 
because  the  blast  cools  off  the  hard,  unmelted  clinkers  of  clay 
and  silex  around  the  tuyere.  If,  in  such  cases,  we  select  a  clay 
which  contains  iron,  or  any  matter  capable  of  melting  the  clay 
at  a  low  temperature,  then  such  a  flux,  melting  at  a  high  point  in 
the  stack,  will  meet,  in  its  descent  through  the  hot  fuel,  the  heated 
calcareous  ore,  and,  combining  with  the  lime,  liberate  the  iron, 
which  is  then  at  liberty  to  descend.  A  part  of  the  iron  will  be 
retained  by  the  imperfectly  melted  lime  and  flux  ;  but,  on  coming 
in  contact  with  the  more  concentrated  heat  of  the  hearth,  it  will 
be  separated. 

t.  From  the  foregoing  demonstrations,  we  are  enabled  to  draw 
conclusions  relative  to  the  economical  working  of  the  ores.  It 
follows,  from  what  we  have  stated,  that  clay  ores  are,  of  all  ores, 
the  most  profitable,  because  of  the  facility  with  which  they  absorb 
carbon,  and  because  of  the  low  temperature  at  which  they  precipi- 
tate iron;  but  the  refractory  character  of  their  admixtures  prevents 
us  from  deriving  those  advantages  from  them  which,  under  other 
circumstances,  they  would  furnish.  Silicious  ores  do  not  absorb 
carbon  so  readily ;  but  the  foreign  matter  which  they  contain  is 
more  inclined  to  form  liquid  compounds  with  lime  or  iron,  and  to 
liberate  the  revived  iron.  On  this  account,  they  are  more  manage- 
able than  the  clay  ores.  Notwithstanding  the  tendency  of  silicious 
ores  to  smelt  white  iron,  the  fusibility  of  their  admixtures,  in  con- 
tact with  alkalies,  gives  them  precedence  over  the  clay  ores  for 
the  smelting  of  gray  or  foundry  metal.  Calcareous  ores  do  not  con- 
dense carbon,  if  the  amount  of  lime  in  the  admixture  is  large ;  but 
if  the  amount  is  small,  they  condense  carbon  like  the  pure  peroxide 
of  iron.  However,  they  will  not  retain  it  absorbed,  because  the 
iron  revived  is  not  very  liquid.  The  carbon  is  retained  in  the  ore 
until  exposed  to  the  influence  of  blast,  when  it  disappears.  It  is 
a  well-known  fact  that  ores  containing  much  lime  in  admixture  do 
not  produce  gray  iron  with  facility,  and  consume  more  fuel  than 
any  other  ores. 

u.  What  is  the  cause  of  the  difference  in  the  capacity  of  matters 
to  absorb  and  retain  carbon  ?  For  the  solution  of  this  question 
we  must  refer  to  chemistry.  But  so  important  is  this  subject  to 
the  iron  manufacturer,  that  we  shall  offer  no  apology  for  direct- 
ing, as  briefly  as  possible,  his  attention  to  it.  Observation  has  un- 
questionably proved  that  clay  possesses  the  power  of  condensing 


REVIVING  OF  IRON.  223 

carbon  in  the  highest  degree;  and  that  there  is  scarcely  any  matter 
so  little  disposed  to  absorb  and  retain  carbon  as  lime.  As  a  car- 
bonate, lime  will  absorb  carbon,  but  not  as  burnt  or  quick-lime. 
This  may  be  caused,  in  part,  by  chemical  affinity ;  but  there  is 
no  question  that  it  is,  to  some  extent,  caused  by  the  mechanical 
form  of  the  particles  of  matter ;  otherwise  the  difference  between 
clay  and  silex  would  not  be  so  great.  There  is  no  doubt  that  the 
same  power  which  retains  the  carbon  retains  the  iron.  The  particles 
of  clay  are  very  minute ;  so  also  are  the  particles  of  the  oxide  of 
iron  mixed  with  clay.  When  carbon  penetrates  the  pores  of  such 
a  mixture,  and  heat  is  applied,  a  part  of  the  metal  is  retained  in  the 
interior  of  the  ore  fragment.  The  particles  of  silex  are  coarser  than 
those  of  clay ;  and  if  the  affinity  of  silex  for  carbon  were  so  great  as 
that  of  clay,  it  could  not  retain  so  much  iron  as  the  latter,  because  of 
its  coarse  grain.  From  this  quality,  added  to  the  other  facilities 
which  it  possesses  of  reviving  iron,  it  may  be  considered  a  more 
profitable  ore  than  the  above.  Lime,  in  its  aggregate  form,  is  very 
fine-grained;  but  it  does  not  absorb  any  carbon,  and  for  that  reason 
the  iron  is  refractory,  that  is,  it  cannot  separate  from  the  lime  at 
a  low  heat.  The  iron  is  not  sufficiently  liquid  thus  to  separate, 
and  is  retained  until  the  lime,  becoming  fluxed,  leaves  it. 

v.  For  these  reasons,  we  are  convinced  that  rich  ores  consume 
a  great  deal  of  fuel,  and,  on  this  account,  are  not  so  good  as  some 
poorer  ores.  If  the  disadvantages  of  their  use  are  not  compensated 
by  cheap  fuel,  and  by  the  production  of  a  good  quality  of  metal,  it 
is  not  advisable  to  smelt  them  by  themselves.  Calcareous  ore  is 
equally  expensive,  so  far  as  the  consumption  of  fuel  is  concerned ; 
and,  if  smelted  by  itself,  is  little  apt  to  produce  good  iron.  The 
same  remark  applies,  to  nearly  the  same  extent,  to  silicious  ore. 
Clay  ore,  if  poor,  would  not  produce  any  iron,  if  smelted  without 
fluxes.  It  thus  clearly  appears  that  no  iron  ore,  of  whatever  de- 
scription, is,  smelted  by  itself,  so  profitable  as  it  would  be  when 
mixed  with  other  ores. 

The  iron  which,  in  the  clay  ore,  is  so  readily  carbonized,  will  not 
separate  from  its  foreign  matter  until  that  matter  is  absorbed  by 
another  element  which  has  the  power  of  liquefying  it.  This  is 
also  the  case  with  silicious  and  calcareous  ores.  Rich  ores  do  not 
smelt  well,  because  their  pores  have  no  opportunity  of  absorbing 
carbon  at  a  low  temperature;  therefore,  these  ores  are  not  pre- 
pared for  reduction  when  they  arrive  in  the  neighborhood  of  the 


224  MANUFACTURE  OF   IRON. 

tuyere.  The  rich  ores  receive  and  absorb  carbon,  and  produce 
iron,  by  flowing  in  a  semi-liquid  slag  through  a  column  of  hot  coal 
of  greater  or  less  height,  according  to  the  quality  of  the  ore.  These 
considerations  lead  us  to  the  construction  of  the  interior  of  the  blast 
furnace,  and  to  the  development  of  the  principles  by  which  its  form 
and  dimensions  are  determined. 

Applying  these  principles,  we  should  build  a  furnace  without  a 
hearth,  that  is,  by  sloping  the  boshes  down  to  the  tuyere,  in  case  it 
is  our  intention  to  smelt  rich  ores;  and  we  should  make  a  partial  or 
complete  hearth  above  the  tuyere,  according  as  facilities  presented 
themselves  of  mixing  the  rich  ore  with  poorer  ores  of  the  proper 
kind.  If  we  could  bring  the  mixture  to  an  advantageous  standard, 
we  should  employ  a  narrow  or  high  hearth,  with  the  object  of  econo- 
mizing fuel,  of  obtaining  a  better  yield  from  the  ore,  and  of  smelting 
gray  iron.  Any  alterations  required  should  be  made  in  conformity 
to  these  considerations.  If  we  arrive  at  conclusions  too  hastily,  we 
shall  have  the  mortification  of  finding  that  our  anticipations  will  not 
be  realized,  and  we  shall  be  under  the  necessity  of  returning  to  the 
original  form.  The  form  we  have  suggested,  that  is,  a  furnace  with- 
out a  hearth,  owes  its  importance  to  the  necessity  which  exists  of 
raising  the  temperature  of  the  whole  stack  to  a  high  degree,  because, 
unless  there  is  a  high  column  of  hot  coal,  the  melted  ore  will  not  be 
affected  by  carbon.  This  rule  is  also  to  be  applied  to  calcareous 
ore.  For  silicious  and  clay  ores  the  hearth  may  be  high,  and  the 
boshes  flat.  These  ores  absorb  carbon  in  proportion  to  the  coolness 
of  the  upper  part  of  the  furnace.  When,  after  being  saturated  with 
carbon,  they  arrive  in  the  narrow  part  of  the  hearth,  the  intense 
heat  of  the  crucible  will  melt  the  iron  and  the  foreign  matter 
almost  at  the  same  moment.  If  the  foreign  matter  is  fluxed,  the 
iron  will  thus  be  precipitated  in  the  shortest  possible  manner. 

From  these  investigations  we  have  arrived  at  the  conclusion, 
theoretically,  that  no  ore  is  perfect.  This  conclusion  is  confirmed 
by  practice.  The  magnetic  are  not  the  most  profitable  ores,  because 
of  the  amount  of  fuel  they  consume.  The  same  remark  applies  to 
the  compact  oxides,  to  calcareous  ore,  and  to  silicious  and  clay  ore. 
For  this  reason,  the  latter  do  not  yield  well.  By  mixing  the  various 
kinds  of  ore,  the  virtues  of  one  will  counterbalance  the  imper- 
fections of  another.  The  desideratum  is  to  find  a  proportional 
admixture  united  in  a  native  ore.  In  practice,  the  ores  are  mixed 
in  a  certain  ratio  artificially.  This  conclusion  leads  naturally  to 


REVIVING   OF   IRON.  225 

the  inquiry  concerning  the  different  portions  of  each  kind  of  ore, 
and,  consequently,  to  the  constitution  of  cinder. 

w.  It  will  be  clear  to  every  discerning  mind,  after  reading  the 
above,  that  the  knowledge  of  the  composition  of  the  foreign  matters 
in  the  ores,  which,  when  melted  together,  constitute  cinder,  and  the 
knowledge  of  the  circumstances  under  which  the  most  favorable 
results  can  be  obtained,  are  highly  valuable.  Iron,  under  certain 
conditions,  can  be  melted;  if  protected  against  oxygen,  it  is  un- 
affected by  heat.  Like  other  metals,  it  is  more  fusible  when  an 
alloy  is  combined  with  it ;  it  is  most  fusible  when  combined  with 
phosphorus,  sulphur,  or  carbon.  The  latter  element  is  preferable, 
because  phosphorus  and  sulphur  are  considered  injurious  to  the 
quality  of  the  metal.  We  are  thus  led  to  conclude  that,  if  iron 
could  be  combined  with  carbon  under  all  circumstances,  it  would 
be  equally  liquid,  no  matter  from  what  kind  of  ore  it  has  been 
smelted.  This  conclusion  is  true :  but  we  have  seen  that  some  ores 
will  not  make  carburetted  iron  at  all;  and  that  others,  which  make 
it  in  abundance,  cannot  precipitate  all  their  iron,  on  account  of 
the  refractory  quality  of  its  admixture.  If  an  admixture  of  ore  is 
just  as  fusible  as  the  iron  itself,  the  iron  and  foreign  matter  will 
separate  spontaneously.  This  will  be  the  surest  and  most  profitable 
way  of  smelting. 

From  this,  it  is  apparent  that  the  appropriate  way  of  proceeding 
will  be,  so  to  combine  different  ores  that  the  iron  and  foreign  matter 
will  melt  at  the  same  moment,  or,  what  is  the  same  thing,  at  the 
same  temperature. 

If  such  a  mixture  is  porous,  it  will  absorb  carbon,  and  offer  a 
chance  of  smelting  by  a  lower  temperature.  If  its  composition  is 
favorable  to  the  absorption  of  carbon,  the  only  difficulty  which 
remains  is  the  production  of  a  cinder  quite  as  liquid  as  the  iron. 
This  is  performed  less  easily  than  we  should  at  first  conceive;  for,  if 
we  compound  the  material  for  the  making  of  cinder,  it  is  only  under 
certain  conditions  that  we  arrive  at  the  best  results;  and  these  con- 
ditions are,  to  a  great  extent,  limited  to  local  elements. 

x.  Mr.  J.  H.  Alexander,  of  Baltimore,  tells  us,  in  his  "  Report 
on  the  Manufacture  of  Iron,"  that  the  difference  in  the  consumption 
of  fuel  varies  according  to  the  fusibility  of  the  ore,  or,  what  is  the 
same  thing,  according  to  the  iron  and  cinder;  and  he  shows  us  that 
the  richest  ores  consume  the  most  fuel.  We  extract  the  following 
table  from  his  Report: — 
15 


226  MANUFACTURE   OF   IRON. 

Table  showing  the  probable  consumption  of  charcoal  per  100  parts 
of  crude  iron,  with  ores  of  different  sorts. 

Denomination.  Proportion  of  metal     Charcoal  consumed 

per  100  metal. 

66  to    90 

Fusible  ores— yielding  ^      30  "  35  90  "  110 

120  "  130 
110  "  140 

Ores  of  mean  fusibility — yielding^      40  "  50  140  "  180 

180  "  220 
160  "  200 

Ores  hardly  fusible— yielding        ^      40  "  50  210  "  250 

250  "  300 

These  results,  applied  to  tons  of  iron  and  bushels  of  coal,  would 
give  us  from  100  to  440  bushels  of  charcoal  per  ton  of  iron. 

To  understand  this  table  properly,  we  may  remark  that  the  above 
amount  of  fuel  will  be  consumed,  if  we  manufacture  gray  iron. 
The  rich  specular  ores,  the  spathic  ores,  &c.,  do  not  consume  much 
fuel,  if  we  are  satisfied  with  white  metal,  and  suffer  a  portion  of  the 
ore,  in  combination  with  the  foreign  matter,  to  form  cinder. 

y.  The  relative  degree  of  fusibility  of  the  cinder  is,  however,  the 
main  point  to  be  gained.  Where  the  cinder  is  too  thick  and  pasty 
below  the  tuyere,  the  iron  globules  cannot  pass  the  blast  without 
injury ;  where  it  is  too  liquid,  it  will  leave  the  iron  too  soon,  and 
thus  expose  the  metal  to  the  influence  of  the  blast.  The  most 
desirable  condition  is  that  in  which  the  cinder  and  iron  have  the 
same  fusibility,  and  arrive  together  in  the  hearth  before  either  is 
sufficiently  heated  for  melting.  If  one  should  be  more  fusible  than 
the  other,  that  one  is  the  cinder.  But  to  secure  this  high  state  of 
fusibility,  and  at  the  same  time  to  smelt  gray  iron,  is  possible  only 
under  very  favorable  conditions. 

The  fusibility  of  earthy  compounds  depends  principally  upon  their 
chemical  relations.  We  do  not  feel  sufficiently  interested  in  this 
highly  intricate  subject  to  enter  upon  its  investigation ;  and  we 
doubt  whether,  after  all,  we  should  derive  from  such  an  investigation 
more  information  than  we  have  already  obtained  from  experience. 
In  most  cases,  artificial  fluxes  are  too  expensive  for  use;  in  fact, 
they  are  unnecessary,  because  we  can  produce  almost  any  degree 
of  fusibility  we  desire  by  means  of  lime,  clay,  and  silex.  All  other 
materials  which  serve  as  fluxes  are  in  quantities  too  small  to  be 
entitled  to  notice,  and  impracticable  for  general  application :  such 


REVIVING   OF   IRON.  227 

as  soda,  potash,  manganese,  and  magnesia.  We  shall  cursorily 
notice  these  materials,  as  they  are  occasionally  employed,  and  as 
they  will  assist  in  the  explanation  of  the  principles  of  fusibility. 

Soda  is  the  most  powerful  solvent  of  silex  or  clay  ;  after  this 
comes  potash,  then  lime,  then  magnesia.  The  alkaline  earths,  as 
baryta,  strontia,  lime,  magnesia,  and  alumina  form  with  silex  very 
refractory  compounds.  If  but  one  of  these  earths  is  combined  with 
silex,  the  compound  is  scarcely  fusible  in  the  strongest  heat  of  the 
blast  furnace.  Such  combinations  exist  as  native  deposits.  Fire 
clay  is  a  compound  of  silex  and  clay,  a  silicate  of  alumina ;  it  will 
resist  a  very  strong  heat.  Soapstone  is  a  silicate  of  magnesia,  and 
also  bears  a  very  strong  fire ;  but  an  excessive  heat  is  not  required 
to  melt  a  mixture  of  pounded  fire  clay  and  pounded  soapstone. 
This  principle  is  the  leading  feature  in  the  art  of  mixing  ores. 

We  see  here  that  silex,  in  combination  with  clay  or  magnesia, 
will  not  melt ;  but  a  mixture  of  a  given  amount  of  alkali,  magnesia, 
and  clay,  with  a  given  amount  of  silex  or  acid,  is  fusible.  If  to  the 
above  two  silicates  we  add  a  third  silicate  in  itself  either  infusible 
or  strongly  refractory,  say  silicate  of  lime,  the  whole  mixture  is 
melted  at  a  lower  temperature  than  that  at  which  any  two  of  them 
will  melt ;  and  if  we  still  add  a  fourth  silicate,  the  fusibility  is  be- 
low the  mean  temperature  of  the  whole  mixture.  That  is  to  say, 
if  the  first  silicate  will  melt  by  itself  at  100°,  the  second  at  90°,  the 
third  at  80°,  and  the  fourth  at  20°,  the  whole,  mixed  together,  will 
melt  below  a  temperature  represented  by  the  sum  of  all  the  tem- 
peratures added  together,  and  divided  by  the  number  of  primary 
silicates.  Thus,  100°+900  +  800  +  20°  =  720  would  be  the  mean; 
but  the  composition  would  melt  below  the  mean  temperature. 

The  fusibility  of  a  binary  compound,  that  is,  a  single  base  and 
silex,  depends  very  much  on  the  degree  of  chemical  affinity  of  the 
two  elements.  As  we  have  before  stated,  soda  and  silex  have  the 
greatest  affinity.  Then  follow  potash,  baryta,  strontia,  magnesia, 
lime,  and  lastly  clay,  in  the  order  of  affinity.  That  is  to  say,  a 
mixture  of  one  pound  of  soda  and  one  pound  of  silex  will  melt  at 
a  lower  temperature  than  a  mixture  of  one  pound  of  clay  and  one 
pound  of  silex.  Or,  if  learned  chemists  are  not  satisfied  with  the 
expression  pounds,  let  us  say  equivalents.  If  the  amount  of  one 
element  increases  too  much,  proportionally  to  the  other,  the  fusibility 
decreases.  There  is  a  limit  in  the  relative  proportion  of  matter  at 
which  the  greatest  fusibility  is  produced.  The  fusibility  of  a  mix- 
ture of  baryta  and  silex  ranges  between  thirty  and  seventy  per 


228  MANUFACTURE   OF  IRON. 

cent.  In  cases  where  the  silex  is  less  than  thirty,  and  more  than 
seventy,  per  cent.,  the  mixture  is  equally  infusible.  So  far  does 
this  law  extend,  that  the  most  fusible  compounds  permit  the  greatest 
range,  and  the  least  fusible  are  confined  to  the  narrowest  limits. 
Potash  is  fusible  by  itself,  and  a  mixture  of  ninety-nine  silex  and 
one  soda  or  potash  is  not  infusible ;  while  the  fusibility  of  a  lime 
silicate  ranges  only  between  twenty-five  and  forty-seven  per  cent, 
of  lime,  and  a  strontia  silicate  is  confined  to  but  one  proportion, 
that  is,  forty-five  strontia  and  fifty-five  silex.  Silicates  of  clay  and 
of  magnesia  are  not  fusible  at  all  in  the  heat  of  a  blast  furnace. 

The  alkalies  proper  and  the  alkaline  earths  are  not  the  only 
elements  which  form  fusible  compounds  with  silex.  The  metallic 
oxides,  in  obedience  to  the  law  of  affinity,  possess  this  attribute  in 
a  higher  degree  even  than  the  alkaline  earths.  The  oxides  of  bis- 
muth, lead  and  iron  especially,  form  fusible  compounds  ;  of  these, 
however,  the  silicates  of  iron  alone  interest  us.  The  protoxide  of 
iron  forms  with  silex  a  very  fusible  compound,  which  reaches  from 
40  to  82  per  cent,  of  protoxide,  and  is  not  far  behind  the  lime. 
Peroxide  of  iron  silicates  are  almost  infusible ;  and  sesquioxide 
silicates,  or  magnetic  oxide  silicates,  range  between  peroxide  and 
protoxide  silicates.  Copper,  zinc,  and  tin  silicates  are  scarcely 
fusible. 

Amongst  the  electro-positive  elements  (the  bases)  of  the  above 
enumerated  compounds,  we  should  pay  particular  attention  to  the 
behavior  of  clay  under  different  circumstances.  Clay  is  not  a 
strong  alkali,  but  possesses  the  remarkable  property  of  becoming 
an  alkali  where  an  alkali  is  needed,  and  of  forming  an  acid  where 
there  is  a  surplus  of  alkali  in  the  composition. 

z.  The  tendency  of  the  alkalies  or  their  carbonates  to  dissolve 
metallic  oxides  is  a  fact  worthy  of  special  notice.  Six  parts  of 
carbonate  of  potash  dissolve  one  part  of  iron  protoxide,  and  car- 
bonate of  iron  is  still  more  soluble.  The  carbonates  of  lime  and 
magnesia  dissolve  protoxide  and  carbonate  of  iron  very  readily. 
Other  metallic  compounds  of  that  kind  are  of  no  interest  to  us. 

Silicates,  or  the  melted  and  liquid  compounds  of  alkalies  and 
silex,  possess  the  property  of  dissolving  metallic  oxides,  and  often 
to  a  large  amount.  Such  solutions  are,  to  a  greater  or  less  extent, 
colored  ;  sometimes  they  are  white.  The  protoxides  of  iron  impart 
a  green  color  to  the  cinder,  and,  if  in  large  quantity,  a  black  color. 
Magnetic  oxide  colors  the  cinder  brown,  and,  when  in  large  amount, 
black.  Peroxide  of  iron  imparts  a  dirty  yellow  or  reddish  color  to 


REVIVING    OF  IRON.  229 

tlie  cinder;  it  is  but  little  soluble.  Carbonate  of  iron  imparts  to 
cinder  a  white  or  yellow  color.  Colors  imparted  by  other  matter 
will  be  mentioned  in  another  place. 

It  may  be  mentioned  that  free  lime,  or  a  surplus  of  lime  in  cin- 
der, possesses  the  property  of  absorbing  sulphur.  Free  alumina,  or 
a  surplus  of  alumina,  if  an  abundance  of  alkali  is  present,  will  ab- 
sorb phosphorus,  and  carry  it  off  in  the  cinders.  The  same  remark 
applies  to  lime. 

After  the  above  consideration  of  the  general  principles  in  the 
formation  of  cinders,  we  are  led  to  inquire,  what  constitutes  a  good 
cinder?  A  positively  good  cinder  is  one  which  is  fusible  at  that 
heat  at  which  the  iron  it  encloses  will  become  liquid.  The  lower 
that  temperature,  the  less  will  be  the  amount  of  fuel  used  in  the 
process  of  smelting.  From  this  it  is  obvious  that  the  fusibility  of 
the  cinder  should  bear  a  certain  relation  to  the  mechanical  form 
and  chemical  composition  of  the  ore.  An  open,  porous  clay  ore 
will  require  the  most  fusible  cinder ;  and  a  calcareous  ore,  a  refrac- 
tory admixture.  Different  degrees  of  fusibility  require  distinct 
compositions  of  cinder  and  of  iron  ;  therefore,  the  cinders  from 
differently  composed  ores,  and  from  different  fuel,  will  require  dif- 
ferent temperatures  for  smelting. 

aa.  The  degrees  of  heat  at  which  iron  containing  more  or  less 
carbon  will  melt,  are  not  accurately  known.  According  to  our  own 
calculations  in  Chapter  II.,  the  fusibility  of  pig  iron  is  not  beyond 
2700°,  because  the  fuel  in  the  blastfurnace  cannot  produce  a  higher 
temperature.  Many  able  observers  have  concluded  that  the  tem- 
perature exceeds  that  point,  but  that  it  is  not  beyond  3000°.  We 
may,  from  these  premises,  conclude  that  the  melting  point  of  the 
different  kinds  of  metal  ranges  between  2000°  and  3000°. 

In  investigations  concerning  the  fusibility  of  silicates,  cinders, 
and  artificial  compounds,  some  very  useful  experiments  have  been 
made,  from  which  we  select  the  following: — 

A  furnace  cinder,  composed  of  silex  50,  alumina  17,  protoxide  of 
iron  3,  lime  30,  melted  at  2576°. 

Another  cinder,  composed  of  silex  58,  alumina  6,  protoxide  of 
iron  2,  manganese  2,  magnesia  10,  lime  22,  fused  at  2500°. 

The  latter  is  a  very  complicated  cinder,  and  ought  to  melt  at  a 
somewhat  low  heat,  but  its  composition  is  of  a  very  refractory  cha- 
racter, as  may  be  observed  from  the  large  amount  of  silex  it  con- 
tains. These  cinders  will  bear  comparison  with  the  anthracite  cin- 
ders of  Pennsylvania. 


230  MANUFACTURE   OF   IRON. 

A  greenish,  rather  dark  cinder,  from  a  charcoal  furnace,  melted 
at  2498°. 

We  shall  have  an  opportunity  of  presenting  further  analyses  of 
cinder  in  the  next  chapter.  It  ought  to  be  remarked  that,  in 
forming  artificial  cinder  from  very  finely  powdered  elements,  the 
temperature  at  which  the  smelting  commences  is  always  from 
500°  to  700°  higher  than  that  at  which  the  cinder  is  kept  liquid. 
The  truth  of  this  remark  is  sufficiently  proved  by  the  refractory 
character  of  the  elements.  Hence  results  the  necessity  of  pound- 
ing the  materials,  as  far  as  practicable.  Where  the  elements  of 
the  ore  are  very  refractory,  the  finest  division  is  required;  but 
where  the  elements  of  a  very  liquid  cinder  are  contained  in  the  ore 
itself,  the  breaking  of  the  ore  requires  no  special  attention. 

bb.  It  is  very  seldom  in  our  power  to  select  an  ore,  for  our  smelt- 
ing operations, 'which  contains  in  itself  the  elements  of  a  good  cin- 
der. Sometimes  we  are  enabled  to  mix  those  ores  which  form  a 
good  cinder,  and  which  flux  each  other;  but  in  most  cases  we  are 
compelled  to  add  a  dead  flux  to  the  ore  we  have  selected.  This  is 
found  to  be  most  profitable  if  we  are  enabled  to  add  limestone  to 
our  ore  charges.  The  reasons  why  limestone  is  the  best  flux  are 
the  following:  For  various  reasons,  we  generally  attempt  to  smelt 
gray  iron.  To  effect  this  object,  it  is  necessary  to  produce,  or  we  at 
least  desire,  a  cinder  but  slightly  more  fusible  than  the  iron  itself. 
Gray  iron  is  most  easily  produced  from  clay  or  silicious  ore,  or 
from  very  porous  oxides.  Where  we  have  a  choice  between  a  clay 
and  a  calcareous  ore,  the  former  should  be  selected,  for  it  offers 
greater  advantages  than  the  latter.  If  a  clay  ore  is  fluxed  by  lime, 
the  lime  will  not  melt  in  the  upper  part  of  the  furnace,  but  will  de- 
scend into  the  hearth  in  its  original  form,  sometimes  burnt  into 
quick-lime,  but  very  often  as  a  carbonate.  Now,  if  prepared  ore  de- 
scends, the  lime  is  ready  to  receive  the  clay  and  silex,  and  the  iron 
is  speedily  separated  ;  the  whole  mass  in  the  hearth,  hot  coal  and 
lime,  through  which  the  ore  and  iron  are  to  pass,  is  favorable  to  the 
reviving  of  the  metal ;  and  should  particles  of  iron  and  foreign  mat- 
ter even  be  melted  together,  there  is  a  chance  that  a  separation  will 
be  effected.  But  this  is  not  the  case  where  calcareous  ore  is  smelted. 
If  the  amount  of  lime  mixed  with  the  ore  is  so  large  as  to  require 
a  flux  of  clay  or  silex  (under  all  circumstances,  clay  is  preferable, 
because  it  contains  a  portion  of  silex),  the  silicious  matter  will  de- 
scend to  the  tuyere,  and  there  wait  for  the  lime;  the  calcareous  ore 
does  not  melt  nor  yield  its  iron  until  it  arrives  at  the  tuyere,  that  is, 


REVIVING   OF  IRON. 


231 


if  the  ore  contains  no  other  matter  which  would  make  it  fusible. 
In  this  case,  the  whole  process  of  forming  cinder  is  accomplished 
very  nearly  before  the  tuyere ;  while  in  the  former  case,  the  pro- 
cess will,  in  most  cases,  commence  higher  up  in  the  hearth. 

ce.  We  have  thus  endeavored  to  explain,  in  as  simple  a  manner 
as  possible,  the  theory  of  the  blast  furnace.  The  composition  of 
cinder,  a  subject  less  easily  understood  by  those  who  have  not 
studied  chemistry,  deserves  our  closest  attention.  To  bring  this 
subject  to  the  comprehension  of  all  who  desire  information,  we  shall 
conclude  this  chapter  by  presenting  a  series  of  applications,  drawn 
from  ore  analyses,  contained  in  "  Rogers'  Report  on  the  Geology 
of  Pennsylvania.1' 

To  convey  a  clear  idea  of  the  specific  object  we  desire  to  accom- 
plish, we  shall  insert  the  following  analysis  of  furnace  cinder,  taken 
from  Mr.  Alexander's  Report.  We  shall  .also  attempt  to  recon- 
struct from  the  ores  of  Pennsylvania  such  cinders  as  are  taken 
from  furnaces  in  Europe. 


CHARCOAL    FURNACES. 

COKE  FURNACES. 

Peroxide  ores. 

Sparry  carbonate  ores. 

Carbonates  of  the 
coal  formations. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Silica 

51.34 

63.6 

31.1 

52.0 

71.0 

37.8  ' 

49.6 

40.6 

43.2 

35.4 

Lime 

21.80 

24.0 

14.1 

30.2 

7.2 

32.2 

35.2 

38.4 

Magnesia 

482 

1.2 

34.2 

5.2 

5.2 

8.6 

15.2 

4.0 

1.5 

Alumina 

15.21 

3.8 

8.9 

5.0 

2.5 

2.1 

9.0 

16.8 

12.0 

16.2 

Prot,  of  iron 

3.73 

1.7 

1.0 

1.6 

5.0 

21.5 

0.4 

10.4 

4.2 

1.2 

Prot.  of  manganese 

1.16 

3.9 

4.4 

4.7 

6.5 

29.2 

25.8 

2.6 

Oxide  of  titanium 

9.0 

Sulphur 

trace 

trace 

1.4 

Phosphoric  acid 

trace 

No.  1  is  an  average  cinder  of  good  iron ;  No.  2  is  derived  from 
a  furnace  smelting  bog  ores ;  No.  3  from  a  Swedish  furnace  ;  No. 
4  from  France;  No.  5  from  Savoy,  and  is  the  result  of  bad  work 
in  the  furnace;  Nos.  6  and  7  from  a  German  furnace — the  first 
when  in  bad,  and  the  latter  when  in  good,  condition ;  this  furnace 
usually  melts  steel  metal,  from  which  German  steel  is  manufactured. 
Nos.  8,  9,  and  10  are  derived  from  coke  furnaces  in  Wales.  The 
latter  specimen  is  said  to  be  taken  from  the  furnace  when  in  bad 
condition ;  it  is  from  the  same  as  No.  8. 

To  imitate  these  cinders,  just  as  they  appear  in  the  above  table, 
would  be  almost  impossible.  But  this  is  not  required.  We  can 


232  MANUFACTURE   OF   IRON. 

arrive  at  the  same  result  by  another  method — a  somewhat  indirect 
one,  to  be  sure,  but  still  tending  to  consummate  the  desired  result. 
There  is  a  law  of  chemistry  which  governs  the  present  case:  namely, 
that  a  certain  amount  of  silex  or  acid  requires  the  saturation  of  a 
certain  amount  of  base,  such  as  lime,  or  magnesia,  or  protoxide  of 
iron,. so  that  no  base  or  acid  be  left  uncombined.  In  such  a  neu- 
tral condition,  the  cinder  will  be  most  fusible.  Now  it  matters  not 
whether  lime  is  replaced  by  magnesia,  by  protoxide  of  manganese, 
or  by  any  given  base ;  but  there  should  never  be  a  large  surplus 
either  of  acid  or  alkali  in  the  furnace,  for  such  a  surplus  will  remain 
refractory,  and  finally  occasion  much  trouble.  The  elements  which 
combine  to  form  a  fusible  cinder  are  the  oxides  of  metals  :  and  the 
amount  of  oxygen  in  the  silex  or  acid  must  be  equal  to  the  amount 
of  oxygen  in*  the  base,  or  it  must  be  present  in  a  proportion  two 
or  three  times  greater,  or  two  or  three  times  less,  than  the  amount 
of  oxygen  in  the  base  ;  that  is  to  say,  the  one  must  be  united  with 
the  other  in  definite  proportions.  An  enumeration  of  the  equiva- 
lents of  the  various  compounds  necessary  to  be  taken  into  considera- 
tion may  be  found  in  any  handbook  of  chemistry.  In  the  fore- 
going, as  well  as  the  following  demonstration,  we  must  not  be  under- 
stood to  say  that,  with  the  saturation  of  the  silex  by  different  alka- 
lies, the  degree  of  fusibility  is  the  same ;  but  that  the  saturation 
to  which  we  allude,  is  a  neutralization  by  which  a  surplus  either  of 
alkali  or  acid  is  prevented. 

In  the  above  table,  the  average  cinder,  No.  1,  may  be  considered 
a  fair  specimen  for  imitation.  For  practical  purposes,  it  is  not 
necessary  that  the  equivalents  should  be  numerically  correct.  A 
small  surplus  of  oxygen  in  either  respect  should  not  be  considered 
very  injurious.  Should  we  wish  to  imitate  cinder  No.  1  at  a  char- 
coal furnace  situated  near  the  canal,  Westmoreland  county,  Pa., 
we  shall  find  that,  at  that  locality,  the  main  body  of  ore  is  of  the 
argillaceous  kind.  A  specimen  of  this  ore,  taken  near  Blairsville> 
exhibited,  according  to  an  analysis  of  Prof.  Rogers,  the  following 
composition  in  100  parts  : — 

Carbonate  of  iron           -  •      -  71.19 

Carbonate  of  lime                     ...  3.50 

Carbonate  of  magnesia  2.72 

Alumina                 2.10 

Silica    -                  -                           -  17.55 

Water,  &c.    -        -        -        -        -        -  2.94 


REVIVING   OF   IRON.  233 

We  are  not  concerned,  at  present,  -with  the  iron  and  water,  but 
•with  the  other  ingredients.  The  proportion  of  the  silex  in  the  ore  is 
only  17.55 ;  but  the  table  above  presented  calls  for  51.84.  We 
must,  therefore,  multiply  all  other  oxides  by  the  number  resulting 
from  the  division  of  51.84  by  17.55,  which  is  2.9.  Alumina 
2.10  x  2.9  =  6.09,  which  leaves  a  deficiency  of  15.21  —  6.09  = 
9.12  alumina.  Carbonate  of  magnesia  is  composed  of  44.69  mag- 
nesia and  35.86  carbonic  acid.  We  assume  it  to  be  a  subcar- 
bonate,  which  is  generally  the  case;  then  the  amount  of  caustic 
magnesia  in  this  specimen  of  ore  will  be 

/(44.69  +  35.86)  :  2.72  =  44.69  :  :A  x  2.9  =  3.77. 

But  we  want  4.82  magnesia;  therefore  a  deficiency  of  4.82  —  3.77 
=  1.05  magnesia  is  left.  Carbonate  of  lime  is  a  compound  of 
56  lime  and  44  carbonic  acid.  In  the  table,  the  proportion  of  lime 
is  21.80.  The  ore  contains  but  3.50  carbonate  of  lime;  thus 
making 

/(56  +  44)  :  3.50=56  :  x\  x  2.9  =  5.99: 

therefore  there  is  a  deficiency  of  21.80  —  5.99  =  15.81  lime.  Tak- 
ing the  whole  15.81  lime,  1.05  magnesia,  9.12  alumina,  a  small 
quantity  of  iron  and  manganese  is  yet  required.  The  ashes  of  the 
fuel  will  deliver  a  portion  of  the  alkaline  matter,  but  its  quantity  is 
comparatively  small ;  and  our  labors  would  be  unnecessarily  compli- 
cated if  we  should  take  that  into  account.  Our  next  object  should 
be  to  find  a  mineral  flux  which  contains  whatever  matter  we  need. 
"No  useful  purpose  will  be  served  by  mixing  the  ore  with  another 
from  the  same  neighborhood;  because  none  can  be  found  which 
contains  the  requisite  amount  of  clay  and  manganese.  In  the  coal 
regions  along  the  canal,  among  the  various  veins  of  different  com- 
position, an  ore  may  be  found  suitable  to  match  the  above.  We 
select  from  Rogers'  Report  an  analysis  of  a  specimen  found  at 
Brighton,  Beaver  county.  As  the  same  strata  of  rock  from  which 
this  specimen  was  taken  are  accessible  at  the  Pennsylvania  canal, 
tnere  is  a  possibility  that  an  ore  like  it,  or  similar  to  it,  may  be 
found  in  its  vicinity.  The  Brighton  ore  contains 

Carbonate  of  iron           ...  4-3.89 

Carbonate  of  manganese                            -  7.20 

Carbonate  of  lime                              -  42.51 

Carbonate  of  magnesia  3.57 

Silex,  &c.      -  0.40 

Loss     - 2.43 


234  MANUFACTURE   OF  IRON. 

The  silex,  in  this  analysis,  may  be  neglected.  If  its  amount  were 
greater,  it  would  be  necessary  to  add  it  to  the  silex  of  the  first  spe- 
cimen, and  correct  the  basic  elements  accordingly;  that  is,  to  add 
to  the  silex  of  the  first  specimen  the  silex  of  the  second,  and  to 
subtract  from  the  lime,  magnesia,  and  alumina,  according  to  the 
ratio  of  the  silex  added. 

In  the  above  specimen,  we  have  42.51  carbonate  of  lime,  which 

will  be  equivalent  to  ((56  +  44)  :  42.51=56  :  x\  x=23.8  lime. 
We  have  also  3.57  carbonate  of  magnesia,  which  is  equal  to 
/(44.69  +  35.S6)  :  3.57=44.69  :  x\  and  X  is  1.59  magnesia. 

The  manganese  amounts  to  4.75.  In  comparing  the  whole,  the 
result  is  as  follows: — 

The  analysis  requires  First  ore.  Second  ore.  Total. 

Silex                            51.84  51.84  =  51.84 

Lime                            21.80  5.99  +     23.8       =  29.79 

Magnesia                        4.82  3.77  +       1.59      =  5.36 

Alumina'  15.21  6.09  =  6.09 
Protoxide  of  iron  3.73 

Protoxide  of  manganese  1.16  4.75      =  4.75 

The  first  may  be  considered  an  argillaceous,  inclining  to  a 
silicious  ore,  and  the  second  a  true  calcareous  ore.  Each  of  these 
ores  fluxes  the  other  almost  completely,  at  least  sufficiently  for  every 
practical  purpose.  The  mixture  of  these  two  ores  would  work  ex- 
ceedingly well,  and  readily  produce  gray  foundry  metal;  with 
greater  facility  even  than  the  original  or  model  cinder  in  the  table 
of  Mr.  Alexander.  But  the  metal  thus  produced  would  not  be  so 
strong  as  that  smelted  by  the  model  cinder ;  neither  would  it  be  so 
well  adapted  to  produce  forge  metal,  because  of  the  deficiency  of 
alumina  in  the  Bolivar  ore.  These  ores  should  be  mixed  in  the  ratio 
of  2.9  of  the  first  to  one  of  the  latter;  the  resulting  mixture  would 
yield  30.1  per  cent,  of  iron,  for  the  first  ore  contains  34.37,  and  the 
second  20.79,  per  cent,  of  iron. 

If  no  calcareous  ore  can  be  found  at  a  reasonable  price,  a  dead 
flux,  such  as  lime,  should  be  employed.  The  first,  or  Bolivar  ore, 
contains  clay  in  quantity  rather  too  small  to  make  forge  metal,  but 
in  quantity  sufficiently  large  to  produce  foundry  metal.  If  it  is  our 
design  to  smelt  the  former,  an  addition  of  clay,  or  of  limestone 
which  contains  clay,  should  be  preferred  to  pure  limestone.  In  the 
regular  limestone  strata  of  that  region,  limestone  which  contains 
even  one  or  two  per  cent,  can  scarcely  be  found ;  but  in  the  shale 


REVIVING   OF  IRON.  235 

strata  of  the  same  region,  there  exist  small  deposits  of  an  argil- 
laceous limestone  called  cement  lime.  From  these  sources,  a  pro- 
fitable flux  for  the  above  ore  may  be  obtained. 

dd.  In  Mr.  Alexander's  table,  cinder  No.  3  is  taken  from  a 
Swedish  furnace:  this  cinder  is  remarkable  on  account  of  the  large 
amount  of  titanium  which  it  contains;  titanium  is  generally  the  com- 
panion of  magnetic  ores.  A  similar  ore  exists  at  Lake  Champlain  in 
large  quantities,  the  working  of  which  is  different  from  that  of  most 
other  ores.  We  shall  therefore  make  some  remarks  on  this  subject, 
for  not  only  the  Lake  Champlain  ores,  but  most  of  the  magnetic  ores 
of  New  York,  Wisconsin,  and  Missouri,  contain  titanium.  It  is  said 
that  the  above  ore  contains  11  per  cent,  of  oxide  of  titanium  ;  this 
will  account  as  well  for  the  many  difficulties  encountered  in  smelt- 
ing it,  as  for  the  great  expenses  incurred  in  manufacturing  iron 
from  it.  Titanium,  or  titanic  acid,  neither  benefits  the  iron  ore  nor 
injures  the  metal  manufactured  from  it;  still,  it  may  occasion  much 
trouble  in  the  furnace.  It  does  not  combine  with  iron,  silex,  lime, 
potash,  or  anything  else;  avoiding  all  connection  with  contiguous 
atoms,  it  associates  neither  with  the  individuals  of  the  alkaline  nor 
with  those  of  the  acid  series.  Still  there  is  a  way  of  getting  rid 
of  this  exceedingly  troublesome  substance,  that  is,  by  letting  it  go 
with  the  masses  of  cinder.  Titanic  acid  does  not  melt  by  itself,  nor 
with  anything  else.  If  present  to  the  amount  of  ten  per  cent,  in  the 
ore,  a  neutral  matter,  amounting  to  330  pounds,  will  thus  exist  in 
every  ton  of  iron,  that  is,  if  we  take  only  a  ton  and  a  half  of  ore 
to  the  ton  of  metal ;  but,  on  an  average,  two  tons  of  ore  are  re- 
quired to  produce  a  ton  of  metal.  If  but  a  tenth  part  remains  in 
the  furnaces,  it  will  speedily  accumulate,  and  obstruct  the  passage 
of  the  cinder;  and  this  obstruction  no  heat  can  remove.  Prot- 
oxide of  iron,  though  in  a  very  low  degree,  and  its  isomeric  com- 
pounds, are  solvents  of  titanium;  but  the  quantity  required  for  this 
purpose  is  so  large  that  we  cannot  think  of  making  use  of  them 
in  the  blast  furnace.  On  this  principle  the  Catalan  forge  is  con- 
ducted ;  the  titanium  of  the  ore  is  carried  off  by  the  subsilicates  of 
that  process.  At  the  blast  furnace,  all  our  endeavors  are  directed 
to  the  extraction  of  every  particle  of  iron  from  the  ore.  We  thus 
act  in  a  manner  precisely  the  reverse  of  that  in  which  we  ought 
to  act  in  this  case.  Instead  of  being  indifferent  concerning  the 
loss  of  a  small  quantity  of  ore,  the  heat  is  increased,  and  most  of 
the  iron  revived ;  while  the  titanium,  thus  deprived  of  all  chance 
of  leaving  the  furnace  peaceably,  remains  with  some  of  the  cinder 


236  MANUFACTURE   OF   IRON. 

as  a  cold,  pasty  mass,  which  the  hottest  blast  will  not  soften  into 
a  fluid  slag. 

ee.  If  we  wish  to  revive  most,  or  all  of  the  iron,  in  cases  where 
titanium  is  the  enemy  against  which  we  have  to  contend,  our  most 
successful  plan  of  operation  is  to  increase  the  foreign  matter,  and 
to  form  a  large  quantity  of  a  more  or  less  fusible  cinder,  according 
to  the  quality  of  metal  to  be  made.  In  this  case,  as  in  other  cases, 
it  is  not  advisable  to  employ  pure  silex,  or  pure  clay  or  lime ;  but 
to  select  ferruginous  clay,  ferruginous  slate,  or  lime  containing  iron. 
Pure  lime  and  pure  clay  are  injurious  in  every  instance.  Titanium 
is  subject  to  the  general  law  of  the  solubility  of  the  oxides  of  metals 
in  silicates ;  and  the  more  fusible  such  silicates  are,  or  the  lower 
the  temperature  at  which  they  melt,  the  greater  is  their  dissolving 
power.  Hence,  where  the  amount  of  titanium  is  large,  the  amount 
of  cinder  should  be  uncommonly  large,  to  produce  gray  iron;  but 
if  we  are  indifferent  about  the  loss  of  a  little  ore,  and  smelt  white 
forge  metal  at  a  low  temperature,  the  fluxing  of  the  furnace  requires 
but  little  foreign  matter.  Ores  containing  titanium  may  be  con- 
sidered very  favorable  for  the  manufacture  of  steel  metal;  in  many 
respects,  they  are  preferable  to  the  spathic  ores ;  for,  with  very  little 
attention,  they  will  produce  white  iron  with  a  large  amount  of 
carbon,  the  very  material  from  which  German  steel  is  manufactured. 
For  this  purpose,  a  high  stack,  and  a  low  hearth,  or  none  at  all, 
like  the  Styrian  furnaces,  are  required  ;  as  well  as  the  addition  of  a 
flux  which  shall  carry  off  the  titanium.  A  sandstone  hearth  would 
not  answer  so  well  as  a  hearth  of  granite  and  gneiss. 

ff.  Cinders  No.  4  and  No.  5  possess  but  little  interest ;  but  Nos. 
6  and  7  are  taken  from  a  furnace  of  which  we  have  personal  know- 
ledge. This  furnace  is  known  to  produce  a  first  rate  article,  from 
which  German  steel  for  the  Solingen  market  is  manufactured.  No. 
6  was  taken  while  the  furnace  labored  under  too  heavy  a  burden  ; 
the  metal  produced  was  white,  serviceable  for  the  manufacture  of 
bar  iron.  No.  7  was  derived  from  the  furnace  when  in  good 
order,  and  while  smelting  gray  iron,  a  kind  of  foundry  metal.  But 
for  this  purpose  the  furnace  is  seldom  employed ;  because  the  re- 
gion in  which  it  is  situated  abounds  in  rich  spathic  ore,  and  sup- 
plies no  ore  of  inferior  quality.  This  rich  spathic  ore  is  scarcely 
at  all  adapted  to  produce  soft  gray  iron.  From  the  same  furnace 
we  have  a  third  specimen  of  cinder  from  a  different  source ;  this 
cinder  was  made  when  the  furnace  was  smelting  steel  metal,  that 
is,  a  white,  crystallized  metal,  containing  a  great  deal  of  carbon. 


REVIVING   OF  IRON.  237 

As  the  manufacture  of  steel  metal  is  carried  on,  in  this  country, 
only  to  a  very  limited  extent,  notwithstanding  we  possess  ore  and 
fuel  in  abundance"  sufficient  to  relieve  us  from  the  tribute  we  at 
present  pay  to  Europe  for  steel,  we  shall  make  some  remarks  which 
may  be  useful  to  those  who  design  to  engage  in  its  manufacture. 
"VVe  shall  call  the  following  specimen  of  cinder  No.  12: — 

Silex  -  48.39 
Lime                                                                           " 

Magnesia  -  10.22 

Alumina  -       6.66 

Protoxide  of  iron       -  -         .06 

"        "  manganese  -                           -  33.96 

The  ore  employed  in  cinders  Nos.  6,  7,  and  12  was  of  the  same 
composition.  Nothing  but  its  burden  was  changed.  In  No.  6  it 
was  heaviest ;  in  No.  7  lightest.  It  will  be  observed  that  there  is 
a  considerable  increase  of  silex  from  No.  6  to  Nos.  12  and  7.  No. 
7  contains  the  largest  amount  of  silex,  but  scarcely  any  iron.  The 
iron  contained  in  No.  6  is  replaced  by  magnesia,  alumina,  and 
manganese.  Scientific  investigation  shows  us  that  the  cinder  from 
gray  iron  contains  fifty  per  cent,  more  oxygen  in  its  silex,  in  pro- 
portion to  the  oxygen  of  the  alkali,  than  the  cinder  from  white  iron, 
No.  6,  contains ;  the  latter  is  almost  a  single  silicate,  in  which  the 
oxygen  in  the  acid  is  equal  to  the  oxygen  in  the  alkali. 

The  characteristic  feature  of  cinder  No.  12  is  that  it  contains  no 
lime.  This  is  an  important  circumstance.  The  lime  is  replaced 
by  manganese ;  but  we  cannot  expect,  in  every  instance,  to  find 
manganese  in  quantities  sufficiently  large  to  flux  the  cinder.  This 
remark  applies  especially  to  the  magnetic  ores  of  this  country. 
Therefore,  if  we  wait  until  we  find  an  ore  which  can  be  fluxed  by  the 
manganese  it  contains,  before  we  succeed  in  manufacturing  steel, 
we  shall  be  under  the  necessity  of  waiting  a  long  time. .  An  addi- 
tion of  black  manganese  will  be  highly  serviceable  ;  but  this  can 
be  only  partially  applied ;  partly  on  account  of  its  expense,  and 
partly  because  of  the  limited  quantity  in  which  it  is  found.  Neither 
lime,  magnesia,  nor  any  of  the  alkaline  earths,  are  of  any  use. 
Protoxide  of  iron  is  inefficient,  because,  in  spite  of  all  our  efforts, 
it  will  be  dissolved  by  the  temperature  of  the  furnace,  and  the 
amount  of  carbon  present.  The  only  resource  which  remains  is 
the  alkalies  proper,  that  is,  potash  or  soda.  Soda  is  preferable  to 
potash,  as  we  shall,  in  the  following  chapter,  more  fully  show. 


238  MANUFACTURE    OF  IRON. 

Lime,  in  this  instance,  does  not  answer  the  purpose  of  a  flux, 
for  the  following  reasons:  Metal  adapted  for  the  manufacture  of 
German  steel  should  contain  a  large  amount  of  carbon,  and  be  as 
free  as  possible  from  foreign  matter;  these  are  objects  accomplished 
with  great  difficulty  in  the  blast  furnace.  We  are  enabled  to  com- 
bine a  large  amount  of  carbon  with  iron,  in  the  blast  furnace  ;  as 
in  the  case  of  gray  anthracite  iron,  or  the  charcoal  iron  of  Hanging 
Rock.  But  this  object  is  always  effected  by  means  of  a  strong, 
silicious  cinder ;  and  such  iron  contains  a  large  amount  of  silex. 
But  this  iron,  though  an  excellent  forge  metal,  is  not  adapted  for 
the  manufacture  of  steel. 

The  combination  of  the  revived  metal  with  carbon  may  be  ef- 
fected with  comparative  facility,  as  we  have  before  demonstrated. 
But  in  the  present  case,  we  need  a  metal  free  from  foreign  matter; 
therefore  it  is  requisite  that  we  employ  an  ore  as  free  as  possible 
from  foreign  matter.  We  have  an  abundance  of  such  ores  in  this 
country  from  Maine  to  Alabama,  and  from  Iowa  to  Texas ;  but  the 
usual  method  of  conducting  blast  furnace  operations  will  not  enable 
us  to  produce  the  required  metal.  Silex  and  clay,  if  they  are  pre- 
sent in  the  ore,  do  no  harm  to  the  metal ;  but  lime  is  injurious. 
Lime  facilitates  the  reviving  of  iron  in  a  higher  degree  than  any 
other  alkali.  While  it  protects  the  bright  surface  of  the  metal,  it 
will  prevent,  and  sometimes  even  dissolve,  the  combination  of  iron 
and  carbon.  For  these  reasons,  lime  is  inapplicable  to  our  purpose. 
Still  another  reason  is,  that  the  affinity  of  lime  for  silex  is  not  suffi- 
ciently strong  to  prevent  the  combination  of  silex  and  iron  :  and  in 
the  presence  of  a  surplus  of  carbon,  silex  will  be  reduced  to  silicon, 
and,  combining  with  the  iron,  will  make  it  brittle,  and  useless  for 
the  manufacture  of  steel. 

The  application  of  soda  or  potash  in  furnace  operations,  as  a 
means  of  fluxing,  has  been  recommended  by  various  writers ;  but 
we  are  not  aware  that  a  successful  experiment  has  ever  been  made. 
While  the  application  of  these  fluxes  will  improve  the  metal  for  the 
forge,  it  will  impair  its  malleability  as  a  foundry  metal. 

gg.  The  hearth  and  in-wall  of  a  furnace  suitable  for  the  manufac- 
ture of  steel  require  a  thoroughly  different  construction  from  those 
of  ordinary  furnaces.  The  material  employed  at  common  furnaces 
cannot  resist  the  action  of  strong  alkalies ;  but  of  the  material  of 
which  a  hearth  should  be  constructed,  we  shall  speak  in  the  next 
chapter.  A  different  internal  form  from  that  of  common  furnaces 


REVIVING   OF   IRON.  239 

is  required.  The  interior  should  be  high ;  there  should  be  no  hearth, 
or  a  very  low  one.  The  blast  should  not  be  too  strong,  but  in 
abundance.  Very  rich  ores  are  desirable,  in  case  artificial  flux  is 
to  be  employed,  for  expenses  will  augment  in  proportion  to  the 
amount  of  foreign  matter  contained  in  the  ore.  It  is  worthy  of 
remark,  that  steel  metal  can  be  manufactured,  so  far  as  charcoal  is 
concerned,  at  a  very  small  cost;  for,  in  Styria,  where  a  large  num- 
ber of  furnaces  produce  this  metal,  less  fuel  is  consumed  than  in 
any  other  blast  furnaces  in  the  world. 

The  analyses  of  cinders  Nos.  6,  7,  and  12  show  conclusively  that 
cinders  from  the  same  furnace,  from  the  same  ore,  and  produced, 
with  the  exception  of  burden,  under  the  same  conditions,  differ 
greatly  in  composition.  Therefore  we  should  be  cautious  in  draw- 
ing conclusions  from  analyses  of  cinder,  and  avoid  hasty  imitations. 
We  do  not  always  know  to  what  kind  of  work  the  cinder  belongs. 
The  theory  of  the  artificial  composition  of  cinder,  which  has  of  late 
been  so  highly  developed,  may,  while  it  is  useful  to  the  utilitarian, 
seriously  mislead  the  speculator,  who,  in  his  eagerness  to  secure 
profitable  results,  fails  to  examine  whether  his  conclusions  are  drawn 
from  sound  or  insufficient  premises.  The  application  of  theories  is 
accompanied  with  difficulty,  because  the  science  of  the  manufacture 
of  iron  is  far  in  advance  of  the  practice.  The  rules  with  which 
science  has  furnished  us  in  relation  to  the  rudiments  of  the  busi- 
ness have,  thus  far,  been  applied  only  to  a  very  limited  degree; 
therefore,  we  cannot  expect  that  improvements,  based  upon  con- 
ditions thus  incompletely  fulfilled,  will  be  altogether  successful. 
Speculative  minds  are  too  little  disposed  to  notice  slight  imperfec- 
tions; but  these  imperfections  constitute  the  greatest  obstacle  to 
the  progress  of  the  business.  Were  they  properly  estimated,  and 
due  pains  taken  to  correct  them,  the  United  States  would  be  enabled, 
in  a  few  years,  to  compete  against  the  world  in  the  manufacture  of 
iron. 

hh.  We  conclude  that  cinder  No.  10,  on  account  of  the  large 
amount  of  lime  it  contains,  produced  red-short  iron  and  white  metal. 
No.  9  is  decidedly  of  better  quality;  and  close  investigation  will 
show  that  this  cinder  produced  gray  metal.  To  enter  into  details 
upon  this  subject  would  probably  be  less  acceptable  to  the  reader 
than  to  present  the  subject  in  as  brief  and  significant  a  manner  as 
possible.  We  infer  that  No.  10  produced  white  iron,  because  the 
amount  of  oxygen  in  the  alkali  is  greater  than  that  in  the  silex; 
whence  it  follows  that  the  cinder  is  a  basic  or  subsilicate.  To  make 


240  MANUFACTURE    OF   IRON. 

gray  metal,  at  least  a  single  silicate,  that  is,  the  presence  of  an  equal 
amount  of  oxygen  in  the  Alkali  and  acid,  is  required.  The  process 
will  be  more  effectual  if  the  amount  of  oxygen  in  the  silex  is  greater 
than  that  in  the  alkali.  This  is  the  case  with  respect  to  No.  9 ;  and, 
in  spite  of  the  large  amount  of  protoxide  of  iron  present,  the  cinder 
is  the  result  of  a  good  quality  of  metal.  If  not  excessively  gray,  it 
is  at  least  goocLfoundry  metal,  made  by  cold  blast.  No.  10  is  a 
peculiar  cinder,  and  is  from  the  same  furnace  as  No.  9.  The  fur- 
nace is  said  to  have  been  in  bad  order;  but  this  cannot  be  true, 
because  the  amount  of  sulphur  in  this  cinder  is  1.4  per  cent.  Nearly 
three  tons  of  cinder,  at  a  coke  furnace,  are  produced  per  one  ton  of 
metal;  therefore,  should  a  good  cinder  have  been  made,  the  iron  of 
No.  9  ought  to  contain  three  times  1.4  per  cent,  of  sulphur.  But 
this  amount  would  render  the  iron  entirely  useless,  even  though  the 
largest  proportion  of  sulphur  present  was  expelled.  Be  this  as  it 
may,  the  coal  or  the  ore  of  the  furnace  at  the  Dowlais  Works,  in 
South  Wales,  contained  a  large  amount  of  sulphur,  which  is  visible 
in  No.  10.  We  allude  to  this  cinder  especially,  because  it  was 
produced  under  conditions  which  resemble  very  closely  those  which 
exist  at  the  Great  Western  Iron  Works,  in  Pennsylvania. 

The  presence  of  sulphur  in  the  furnace  occasions  great  annoy- 
ance. In  the  case  before  us,  the  furnace  required  a  large  charge  of 
limestone  to  produce,  even  at  a  high  temperature,  a  surplus  of 
lime ;  for  this  is  the  best  means  of  carrying  off  a  certain  amount  of 
sulphur.  A  high  temperature  will  produce  a  white  cinder,  streaked 
with  various  shades.  This  cinder  contains,  besides  a  silicate  of 
lime,  a  sulphuret  of  lime,  and  is  characterized  by  soon  losing  its 
lustre  on  being  exposed  to  the  atmosphere.  If,  under  such  circum- 
stances, the  temperature  of  the  furnace  falls  below  a  given  point, 
the  cinder  changes  rapidly  into  a  pitch  black,  heavy  mass,  contain- 
ing a  large  amount  of  sulphuret  of  iron.  The  same  circumstance 
happens  where  too  small  a  quantity  of  limestone  is  used.  In  this 
case,  the  sulphur,  having  no  free  alkali  with  which  to  combine, 
follows  the  iron  into  the  pig  bed,  where  its  presence  is  indicated  by 
the  odor  of  sulphurous  acid.  If  the  furnace  is  cooled  below  the 
temperature  at  which  gray  iron  is  usually  made,  the  cinder,  by 
absorbing  sulphuret  of  iron,  is  soon  blackened.  In  such  cases,  the 
smelting  of  gray  metal  is  accompanied  with  difficulties  which  absorb 
more  attention  than  can  well  be  spared.  In  addition  to  the  difficulty 
of  continuing  a  furnace  on  gray  iron,  the  metal  produced?  is  of  infe- 
rior quality,  and  unsuitable  for  the  market.  To  get  rid  of  the  sul- 


REVIVING  OF  IRON.  241 

phur  is  indispensable,  for,  whether  we  bring  the  pig  iron  to  the 
forge  or  to  the  foundry,  it  is,  in  all  cases,  exceedingly  troublesome. 

There  is  no  resource  left  but  an  excess  of  limestone.  This  will, 
of  course,  produce  white  metal,  and,  if  hot  blast  is  employed,  of 
very  inferior  quality.  In  this  case,  it  is  necessary  to  work  the  fur- 
nace with  light  burden,  to  prevent  the  formation  of  black  cinder, 
which  will  absorb  too  much  iron.  The  revived  iron,  or  iron  ore,  in 
the  upper  part  of  the  furnace,  will  be  saturated  with  carbon  ;  and 
at  the  high  temperature  of  the  hearth,  the  silex,  and  even  the  lime, 
will  be  reduced  to  their  corresponding  metals.  These  metals  will 
combine  with  the  iron  ;  and  having,  where  hot  blast  is  employed, 
little  chance  of  being  oxidized,  they  will  of  course  follow  the  iron 
to  the  bottom,  and  be  troublesome  both  in  the  forge  and  in  the 
foundry.  Metal,  thus  produced,  is  so  brittle  and  hard  as  to  be 
unfit  for  foundry  use. 

We  have  thus  presented  an  instance  in  which  white  iron,  smelted 
by  a  high  temperature,  contains  little  or  no  carbon.  In  charcoal 
furnaces,  on  the  contrary,  the  metal  contains  a  large  amount  of  car- 
bon ;  but  this  applies  only  to  those  cases  in  which  no  limestone,  or 
limestone  in  very  small  quantity,  is  used.  In  this,  as  in  every  case, 
the  disappearance  of  carbon  results  from  the  large  quantity  of  lime 
in  the  furnace.  The  result  is  the  same,  under  similar  circumstances, 
in  charcoal  furnaces.  The  weakness  of  the  metal  is  to  be  attributed 
principally  to  an  admixture  of  silicon,  and  even  of  calcium — both 
very  bad  admixtures — with  the  use  of  hot  blast.  In  this  case,  the 
cold  blast  will  produce  better  metal  than  hot  blast,  because  of  the 
oxidation  of  silex  by  the  former.  By  the  latter  the  oxygen  is  not 
so  quickly  absorbed;  the  iron  which  sinks  is  more  exposed  to 
oxidation ;  and  of  course  calcium,  silicon,  and  carbon  will  be 
sooner  oxidized  than  iron.  But  of  this  matter  we  shall  speak 
hereafter. 

As  we  have  seen,  cinder  No.  10,  compared  with  No.  9,  contains 
very  little  iron.  This  cinder  may  be  considered  the  regular  mixture 
of  ore  and  flux  for  the  location  whence  it  was  derived  ;  because, 
if  it  contained  less  limestone,  the  metal,  in  addition  to  being  very 
hot-short,  would  be  produced  in  very  small  quantity.  A  surplus  of 
limestone  would  produce  a  better  yield,  more  easy  work,  and  metal 
of  good  quality,  however  white  it  might  be.  The  application  of  cold 
blast  in  smelting  is,  so  far  as  the  quality  of  iron  is  concerned,  un- 
doubtedly preferable  to  that  of  hot  blast,  because  of  the  large 
quantity  of  lime  which  is  exposed  to  its  action.  Where  the  blast 
16 


242  MANUFACTURE  OF  IRON. 

is  cold,  the  limestone  will  be  chilled  ;  and  the  cinder  and  iron,  in 
their  passage  through  them,  will  also  become  chilled.  Where  hot 
blast  is  employed,  there  is  a  more  uniform  heat  in  the  hearth,  and 
no  obstacle  prevents  the  passage  of  the  cinder ;  because  even  the 
unmelted  parts  are  sufficiently  warm  to  facilitate  the  process  of 
smelting,  and  the  discharge  of  the  fused  mass. 

From  what  we  have  stated,  we  deduce  the  following  conclusion: 
that  the  best  method  of  using  sulphurous  materials  is  to  smelt  them 
by  an  excess  of  alkalies.  The  resulting  metal  may  be  gray  or 
white.  This  is  both  theoretically  and  practically  true.  We  may 
add,  that  the  smelting  of  sulphurous  minerals  should,  where  prac- 
ticable, be  avoided.  But  where  we  cannot  avoid  using  them,  we 
should  employ  the  hot  blast,  and  work  with  as  low  a  temperature 
as  possible,  with  the  view  of  expelling  silicon.  Any  experiment 
made  with  the  object  of  improving  the  metal  in  the  blast  furnace 
will  be  likely  only  to  augment  the  expenses  of  the  iron  master, 
without  benefiting  his  operations. 

With  these  remarks,  we  shall  conclude  this  chapter ;  trusting 
that  whatever  deficiencies  exist  will  be  supplied  by  the  intelligent 
reader.  We  are  conscious  of  having  omitted  to  state  several  slight 
matters ;  but,  though  these  omissions  will  be  of  little  consequence 
to  an  accomplished  manager,  we  shall,  to  make  our  work  as  com- 
plete as  possible,  notice  them  in  the  following  chapters.  We  flat- 
ter ourselves  that  we  have  mentioned  every  fact  and  theory  which 
has  an  important  bearing  upon  the  successful  operation  of  a  fur- 
nace. 


MANUFACTURE   OF  WROUGHT  IRON. 


243 


CHAPTER    IV. 

MANUFACTURE  OF  WROUGHT  IRON. 

THE  manufacture  of  wrought  iron  involves  two  fundamental 
operations  :  namely,  the  removal  of  impurities  from  the  ore  and 
from  the  crude  metal ;  and  the  oxidation  of  the  metal  to  a  degree 
sufficient  to  form  fibres.  The  first,  which  consists  in  the  removal 
of  impurities,  and  the  vitrification  of  the  earthy  admixtures  in  the 
ore,  is  effected  by  a  variety  of  methods.  If  the  amount  of  im- 
purities in  the  ore  is  large,  an  intermediate  method  is  employed 
to  remove  them  ;  that  is,  metal  of  greater  or  less  purity  is  manu- 
factured in  the  blast  furnace.  But  if  the  amount  of  impurities  is 
excessive,  or  if  the  metal  from  the  blast  furnace  is  very  impure, 
as  is  often  the  case  in  gray  charcoal  pig,  and  quite  generally  the 
case  in  anthracite  and  coke  iron,  the  refining  fire  is  resorted  to, 
before  the  metal  is  subjected  to  the  process  by  which  it  is  converted 
into  bar  or  fibrous  iron.  The  second  operation,  though  effected  by 
a  variety  of  methods  and  by  a  diversity  of  apparatus,  consists  mainly 
in  a  semi-fusion  of  the  metal.  In  this  condition,  it  is  stirred  and 
worked  by  manual  labor,  with  the  object  of  exposing  the  smallest 
particles  of  the  metal  to  the  influence  of  the  atmospheric  oxygen. 

In  this  chapter,  we  shall  endeavor  to  describe  the  principal  forms 
of  apparatus  at  present  in  use  in  various  parts  of  the  world,  and 
especially  in  the  United  States ;  we  shall  attempt  to  indicate  the 
methods  by  which  the  operations  in  the  manufacture  of  wrought 
iron  are  performed ;  and  we  shall  close  the  chapter  by  some  theo- 
retical investigations  to  which  we  would  invite  the  attention  of  the 
manufacturer  no  less  than  the  philosopher. 

I.  Persian  Mode  of  making  Iron. 

The  most  ancient  method  of  manufacturing  iron  is  at  present 
practiced  in  Persia ;  and,  as  far  as  we  can  ascertain  from  the  pub- 
lished reports  of  travelers,  whose  descriptions,  while  they  slightly 
vary  in  detail,  agree  in  relation  to  the  uniformity  of  the  principle, 


244 


MANUFACTURE   OF  IRON. 


this  method  is  practiced  throughout  Asia.  The  manipulation  is  as 
follows  :  A  hearth,  or  a  mould  with  fine  charcoal,  or  clean  charcoal 
dust — that  is,  a  semicircular  hole  from  six  to  twelve  inches  in  depth, 
and  from  twelve  to  twenty-four  inches  in  width,  as  represented  in 
Pig.  71 — is  formed.  The  darker  shading  in  the  figure  illustrates 

Fig.  71. 


Ground-plan  of  a  Persian  forge  fire. 

the  lining  of  charcoal  dust ;  the  form  of  this  lining  is  sometimes 
round,  and  sometimes  square.  Before  the  dust  is  put  into  the 
hearth,  it  is  moistened,  well  mixed,  and  pounded  as  closely  as  pos- 
sible. The  lining  will,  of  course,  be  perfect,  in  proportion  to  the 
fineness  of  the  dust.  The  bottom  especially  should  be  hard,  to 
resist  the  action  of  the  blast.  Into  this  basin,  the  blast  is  conducted 
by  means  of  a  clay  tuyere,  or  a  piece  of  crockery,  situated  a  short 
distance  above  the  bottom  of  the  basin.  The  bellows  are  urged  by 

Fig.  72. 


Asiatic  or  Persian  method  of  making  iron, 

manual  power.  Fig.  72  exhibits  a  section  of  the  basin,  and  the 
situation  of  the  bellows.  In  the  bottom  of  the  basin,  medium-sized 
charcoal  is  laid  to  the  height  of  several  inches,  covered  by  a  layer 


MANUFACTURE   OF   WROUGHT  IRON.  245 

of  ore  in  pieces  of  the  size  of  hazelnuts.  Where  no  compact  ore 
can  be  obtained,  the  fine  ore  may  be  cemented  by  being  moistened, 
and  then  dried  and  broken.  But  the  native  compact  ore  is  prefera- 
ble, because  it  contains  fewer  impurities.  Upon  this  layer  of  ore  a 
layer  of  charcoal  is  placed,  and  then  alternately  ore  and  charcoal 
until  five  or  six  strata  are  piled.  The  whole  is  covered  by  charcoal 
of  moderate  size,  firmly  pounded.  Fire  is  then  introduced  at  the 
tuyere,  and  the  bellows  gently  moved,  so  as  to  expel  all  the  water 
jcontained  in  the  mass,  before  a  full  heat  for  the  reduction  of  the 
ore  is  given.  When  the  water  is  supposed  to  be  driven  off,  the 
bellows  are  urged  more  strongly,  and  the  heat  increased.  The  ore 
is  then  reduced,  and  iron  liberated  in  a  metallic  state.  The  whole 
process  lasts  from  three  to  four  hours,  at  the  end  of  which  time 
twenty-five  or  thirty  pounds  of  iron  may  be  removed  by  tongs,  and 
forged  by  means  of  sledgehammers.  Of  course,  the  desirable 
shape  is  not  produced  until  the  metal  is  heated  and  re-heated  seve- 
ral times.  After  the  iron  from  one  heat  is  forged,  the  clinkers  are 
removed,  and  another  coating  of  charcoal  thrown  on ;  in  fact,  a 
renewal  of  the  whole  process  is  required. 

In  this  process,  none  but  the  best  kind  of  red  iron  ore,  or  specular 
iron,  is  used;  and  it  is  questionable  whether  any  but  the  richest  of 
this  ore  can  be  employed.  The  iron  manufactured  is  very  strong 
and  tenacious;  from  which  the  sabres  of  Damascus,  and  the  neat 
and  delicate,  though  very  powerful  Damascene  gun  barrels,  as  well 
as  weapons  of  nearly  every  kind,  are  wrought.  In  the  States  east 
of  the  Mississippi,  no  ore — or  at  least  no  ore  in  large  quantity — 
suitable  for  the  manufacture  of  such  articles,  is  found ;  but  it  is 
probable  that  it  may  be  obtained  in  Iowa,  Missouri,  and  along  the 
borders  of  the  Rocky  Mountains.  In  Arkansas,  large  deposits 
exist.  This  ore  is  seldom  found  anywhere  else  than  in  transition 
clay  slate,  or  roofing  slate. 

II.   Catalan  Forge. 

This  forge  is  extensively  employed  in  Vermont  and  New  Jersey, 
to  smelt  the  magnetic  ores  of  these  States.  It  is  there  called  the 
blomary  fire.  The  form  of  this  fire  is  nearly  uniform  everywhere. 
Fig.  73  represents  a  Catalan  fire,  seen  from  above.  The  whole  is 
a  level  hearth  of  stonework  from  six  to  eight  feet  square,  at  the 
corner  of  which  is  the  fire-place,  from  twenty-four  to  thirty  inches 
square,  and  from  fifteen  to  eighteen,  often  twenty,  inches  in  depth. 


246  MANUFACTURE   OF  IRON. 

Inside  it  is  lined  with  cast  iron  plates,  the  bottom  plate  being  from 

Fig.  73. 


Ground-plan  of  a  forge  fire. 

two  to  three  inches  thick.      Fig.  74  represefats  a  cross  section 
through  the  fire-place  and  tuyere,  commonly  called  the  iron,     a 

Fig.  74. 


Blomary  fire. 


MANUFACTURE   OF  WROUGHT  IRON.  247 

represents  the  fire-place,  which,  as  remarked  above,  is  of  various 
dimensions.  The  tuyere  b  is  from  seven  to  eight  inches  above  the 
bottom,  and  more  or  less  inclined,  according  to  circumstances.  The 
blast  is  produced  by  wooden  bellows  of  the  common  form,  or,  more 
generally,  by  square,  wooden  cylinders,  urged  by  waterwheels.  The 
ore  chiefly  employed  is  the  crystalized  magnetic  ore.  This  ore 
very  readily  falls  to  a  coarse  sand,  and,  when  roasted,  varies  from 
the  size  of  a  pea  to  the  finest  grain.  Sometimes  the  ore  is  employed 
without  roasting.  In  the  working  of  such  fires,  much  depends  on 
the  skill  and  experience  of  the  workmen.  The  result  is  subject  to 
considerable  variation;  that  is  to  say,  the  result  depends  on  the 
circumstance  whether  economy  of  coal  or  that  of  ore  is  our  lead- 
ing object.  Thus,  a  modification  is  required  in  the  construction 
either  of  the  whole  apparatus,  or  in  parts  of  it.  The  manipula- 
tion varies  in  many  respects.  One  workman,  by  inclining  his 
tuyere  to  the  bottom,  saves  coal  at  the  expense  of  obtaining  a  poor 
yield.  Another,  by  carrying  his  tue  iron  more  horizontally  at  the 
commencement,  obtains  a  larger  amount  of  iron,  though  at  the 
sacrifice  of  coal.  Good  workmen  pay  great  attention  to  the  tuyere, 
and  alter  its  dip  according  to  the  state  of  the  operation.  The  gene- 
ral manipulation  is  as  follows :  The  hearth  is  lined  with  a  good 
coating  of  charcoal  dust;  and  the  fire-plate,  or  the  plate  opposite 
the  blast,  is  lined  with  coarse  ore,  in  case  any  is  at  our  disposal. 
If  no  coarse  ore  is  employed,  the  hearth  is  filled  with  coal,  and  the 
small  ore  piled  against  a  dam  of  coal  dust  opposite  the  tuyere. 
The  blast  is  at  first  urged  gently,  and  directly  upon  the  ore ;  while 
the  coal  above  the  tuyere  is  kept  cool.  Four  hundred  pounds  of 
ore  are  the  common  charge,  two-thirds  of  which  are  thus  smelted ; 
and  the  remaining  third,  generally  the  finest  ore,  is  held  in  reserve 
to  be  thrown  on  the  charcoal  when  the  fire  becomes  too  brisk.  The 
charcoal  is  piled  to  the  height  of  two,  sometimes  even  three  and 
four  feet,  according  to  the  amount  of  ore  to  be  smelted.  When  the 
blast  has  been  applied  for  an  hour  and  a  half,  or  two  hours,  most  of 
the  iron  is  melted,  and  forms  a  pasty  mass  at  the  bottom  of  the 
hearth.  The  blast  may  now  be  urged  more  strongly,  and  if  any 
pasty  or  spongy  mass  yet  remains,  it  may  be  brought  within  the 
range  of  the  blast,  and  melted  down.  In  a  short  time,  the  iron  is 
revived;  and  the  scoriae  are  permitted  to  flow  through  the  tapping- 
hole  a,  so  that  but  a  small  quantity  of  cinder  remains  at  the  bot- 
tom. By  means  of  iron  bars,  the  lump  of  pasty  iron  is  brought 
before  the  tuyere.  If  the  iron  is  too  pasty  to  be  lifted,  the  tuyere  is 
made  to  dip  into  the  hearth.  In  this  way,  the  iron  is  raised  from 


248  MANUFACTURE   OF   IRON. 

the  bottom  directly  before,  or  to  a  point  above  the  tuyere,  until  it  is 
•welded  into  a  coherent  ball  twelve  or  fifteen  inches  in*diameter. 
This  ball  is  brought  to  the  hammer  or  squeezer,  and  shingled  into 
a  bloom,  which  is  either  cut  in  pieces  to  be  stretched  by  a  hammer, 
or  sent  to  the  rolling  mill  to  be  formed  into  marketable  bar  iron. 

a.  A  mixture  of  fibrous  iron,  cast  iron,  and  steel — an  aggrega- 
tion of  unavoidable  irregularities — is  the  result  of  the  above  pro- 
cess.   The  quality  of  the  iron  depends  entirely  upon  the  quality  of 
the  ore.    No  opportunities  are  presented  by  which  any  skill  or  in- 
genuity can  create  improvements  in  this  process.     Poor  ores  cannot 
be  smelted  at  all ;  but  rich  ores,  like  those  at  Lake  Champlain,  or 
in  Missouri,  or  even  the  hydrates  of  Alabama,  may  be  smelted  to 
advantage ;  the  latter  with  a  prospect  of  economy.    In  some  coun- 
tries, where  much  larger  fires  than  the  one  we  have  mentioned  are 
employed,  balls  of  200  or  300  pounds  weight  are  produced ;  but 
such  large  masses  cannot  be  worked  with  facility,  and  are  always 
of  inferior  quality.     It  is  not  advisable  to  make,  at  one  smelting, 
balls  heavier  than  100  pounds. 

In  Vermont,  where  the  rich  magnetic  ores  are  employed  for  this 
kind  of  work,  a  ton  of  blooms  costs  about  forty  dollars.  To  produce 
this  quantity,  four  tons  of  ore  and  three  hundred  bushels  of  char- 
coal are  required.  Wages  of  workmen  per  ton  ten  dollars. 

b.  An  improvement  upon  the  Catalan  forge  is  the  stuck  oven 
described  in  our  third  chapter.     But  little  explanation  is  required 
to  exhibit  the  connection  between  the  two  manipulations.     So 
heavy  are  the  masses  of  iron  in  the  stiick  oven,  that  powerful  ma- 
chinery, as  well  as  a  large  number  of  workmen,  is  required  in 
working  them.    The  salamander,  when  lifted  out  of  the  furnace,  is 
cut  into  pieces  of  100  or  150  pounds  weight.    These  pieces  are  re- 
heated in  a  common  forge,  or  Catalan  fire ;  a  portion  of  the  cast 
iron  melts  out  of  it ;  and  what  remains  is  generally  the  best  iron,  and 
called  the  "blume"  or  flower.     From  this  term  it  is  probable  that 
our  English  word  "  bloom"  is  derived.    Sometimes  the  bloom  is  in 
part  steel,  according  to  the  state  of  the  furnace,  and  the  kind  of  ore 
used;  but,  generally,  it  is  fibrous  iron.    The  cast  iron  which  results 
from  the  re-heating  is  worked,  by  the  common  method,  into  fibrous 
iron.     So  expensive  is  the  operation  in  the  stiick  oven,  and  so  im- 
perfect the  iron  which  it  produces,  that  this  furnace  is  now  generally 
abandoned.    Both  the  Catalan  forge  and  the  stiick  oven  are  imprac- 
ticable where  ores  containing  less  metal  than  forty  per  cent,  are  to 
be  smelted.     Any  foreign  matter  in  the  ore  is  injurious. 


MANUFACTURE   OF  WROUGHT  IRON.  249 

Many  ingenious  contrivances  have  been  devised  to  convert  ore, 
by  one  manipulation,  directly  into  bar  iron  or  steel.  These  con- 
trivances are  local,  and  vary  according  to  the  quality  of  the  ore, 
and  the  intelligence  of  the  operator.  They  are  not  worthy  of  our 
notice ;  in  our  country,  at  least,  they  are  of  no  practical  utility. 

III.   German  Forge. 

The  most  successful  method  of  manufacturing  charcoal  wrought 
iron  is  by  means  of  the  German  refining  forge,  or  the  blomary  fires 
of  Pennsylvania.  These  forges  not  only  produce  good  iron  at 
reasonable  prices,  but  they  afford  all  the  facilities  presented  by 
differently  constructed  apparatus.  Fig.  75  represents  a  section  of 

Fig.  75. 


Forge  fire. 

the  German  forge,  in  which  the  location  of  the  hearth  is  shown. 
The  hearth  is  lined  with  cast  iron  plates ;  the  bottom  is  generally 
kept  cool  by  a  current  of  water  circulating  in  pipes  below  it.  Three 
or  four  inches  above  the  bottom,  there  is  a  row  of  holes,  through 
which  the  cinder  is  let  off.  Through  the  tuyere,  which  is  hollow, 
a  current  of  water  circulates.  Frequently,  the  back  part  of  the 
hearth  is  raised,  for  the  purpose  of  putting  in  hot  air  pipes,  as  shown 


250  MANUFACTURE  OF   IRON. 

at  c,  Fig.  77.     Fig.  75  exhibits  a  better  arrangement  for  heating 
the  blast,     d  represents  a  hollow  roof  plate,  of  sheet  iron,  through 

Fig.  76. 


Forge  fire. 

*vhich  the  blast  passes.     The  blast  for  this  kind  of  fire  is  produced 
either  by  wooden  or  by  iron  cylinder  bellows. 

Fig.  77. 


Heating  the  blast  on  a  forge  fire. 


MANUFACTURE   OF  WROUGHT  IRON.  251 

a.  The  material  employed  in  this  forge  are  the  various  kinds  of 
pig  metal,  from  the  white  pig  which  contains  a  small  amount  of 
carbon,  to  the  gray  and  white  metal  which  contains  carbon  in  con- 
siderable quantity.     The  construction  of  the  apparatus  depends  to 
scarcely  any  extent  upon  the  kind  of  metal  worked.     By  varying 
the  treatment  of  the  material,  in  the  course  of  the  manipulation,  the 
same  results  may,  in  the  great  majority  of  cases,  be  produced. 
Gray  metal  requires  a  higher  heat  at  first  than  white  metal;  besides, 
more  time  is  required,  and  a  greater  amount  of  fuel  consumed,  in 
working  it.     In  this,  as  in  every  case,  white  metal  containing  a 
large  amount  of  carbon  is,  when  smelted  by  hot  blast,  the  worst  of 
all  metals  for  the  manufacture  of  a  satisfactory  iron.     Should  gray 
metal,  smelted  from  the  same  stock  as  white  metal,  by  small  bur- 
den, work  slowly,  and  consume  more  fuel  than  the  latter,  there  is  a 
greater  prospect  of  producing  a  better  article.     An  exception  from 
this  rule  occurs  only  where  ore  of  the  first  quality  is  smelted  by 
charcoal  and  cold  blast.     White  metal,  smelted  by  small  burden 
and  poor  ore,  or  anthracite  or  coke,  is  always  inferior;  it  works  so 
fast  that  no  time  is  afforded  for  the  removal  of  the  impurities  com- 
bined with  it.     Where  gray  metal  is  worked,  a  greater  chance  of 
purifying  the  melted  iron  before  it  comes  to  nature  is  presented. 
These  remarks  do  not  apply  to  white  iron  made  by  charging  the 
blast  furnace  with  a  heavy  burden  of  ore.     At  the  close  of  the 
chapter,  we  shall  speak  at  greater  length  on  this  subject.     In  this 
place,  we  simply  wish  to  draw  the  attention  of  the  manufacturer  to 
this  important  matter;  because  his  success  depends,  in  a  very  high 
degree,  upon  a  clear  understanding  of  the  qualities  of  the  metal, 
and  of  the  modes  of  working  it. 

b.  The  form  of  the  basin  of  the  hearth,  the  height  of  the  tuyere, 
and  the  pressure  and  the  quantity  of  the  blast,  cannot  be  fixed  by 
any  general  rule,  and  depend  on  coal,  metal,  and  the  workmen. 
We  shall  endeavor  to  explain  the  leading  principles  in  each  case; 
but  their  application  is  to  be  varied  according  to  local  circum- 
stances. 

c.  The  quality  of  the  charcoal  determines,  to  a  certain  extent? 
the  dimensions  of  the  hearth,  the  dip  of  the  tuyere,  and  the  pres- 
sure of  the  blast,  as  well  as  the  amount  of  metal  to  be  smelted  by 
one  heat.     Soft  coal,  from  pine  wood  and  poplar,  requires  a  larger 
and  deeper  fire,  a  greater  dip  of  the  tuyere,  and  weaker  blast,  than 
charcoal  from  hickory  and  maple.     Soft  coal  works  more  slowly  than 
hard  coal.     Dirty  or  sandy  coal,  which  has  been  received  from  the 


252  MANUFACTURE   OF  IRON. 

coalings  in  wet  weather,  or  which  has  been  exposed  to  sand  or  mud 
in  the  yard,  should  be  refused  altogether,  or  at  least  carefully  dried 
and  cleaned;  because  each  pound  of  sand  removes  three  or  four 
pounds  of  iron,  for  no  conceivable  purpose  whatever.  Coal  that  is 
not  larger  than  an  egg  will  answer  tolerably  well  for  a  blomary  fire ; 
but  strong  and  heavy  coal  is  far  more  serviceable.  In  the  prepara- 
tion of  coal  for  the  blomary  and  the  blast  furnace,  we  are  guided 
by  different  rules;  that  is  to  say,  the  small  coal  from  the  coalings 
is  taken  to  the  former,  and  the  large  coal  to  the  latter.  It  should 
always  be  remembered  that  coal  which  contains  sand  and  dirt  is 
far  more  injurious  in  the  forge  than  in  the  blast  furnace. 

d.  So  great  are  the  practical  difficulties  in  this  kind  of  work,  that 
fluxes  are  employed  to  a  very  limited  extent.     Hammer-slag  is  some- 
times used  as  a  flux.     This  is  a  very  useful  material ;  it  facilitates 
the  work,  and  improves  the  iron.     Water  is  another  means  of  flux- 
ing.    In  the  first  place,  it  cools  the  iron,  and  thus  gives  the  blast 
a  chance  of  playing  upon  it  to  advantage.     In  the  second  place,  it 
is  decomposed  by  red  hot  iron;  its  oxygen  is  retained,  and  forms 
peroxide  of  iron,  which  readily  combines  with  silex.     For  the  pur- 
pose of  retarding  the  working  of  the  iron,  workmen  are  in  the  habit 
of  throwing  sand,  dry  clay,  or  even  loam  upon  the  fire.     This  is 
inexcusable  ignorance,  or  at  least  gross  sluggishness.     If  proper 
care  and  industry  are  exercised,  the  iron  will  not  come  too  fast,  and 
if  it  does,  the  application  of  sand  will  only  augment  the  evil.     At 
any  rate,  it  is  highly  injurious  to  the  quantity  and  quality  of  the 
iron  produced. 

e.  The  fire-place  is  always  of  a  square  form,  varying  in  size  ac- 
cording to  circumstances,  and  lined  throughout  with  cast  iron  plates. 
To  secure  the  stability  of  the  apparatus,  these  plates  should  be 
well  screwed  together.     The  plate  nearest  to  the  workman,"  called 
the  cinder  or  work-plate,  should  especially  be  solid,  because  a  great 
deal  of  the  manipulation  is  done  on  this  plate.     The  plates  around 
the  fire  are  generally  laid  in  a  somewhat  sloping  position,  more 
for  the  purpose,  we  presume,  of  facilitating  the  lifting  out  of  the 
bloom,  and  of  making  the  dust  stick,  than  for  anything  else.     The 
tuyere  plate  is  generally  inclined  into  the  hearth,  partly  with  the 
object  of  facilitating  the  dipping  of  the  tuyere,  and  partly  with  the 
object  of  cooling  that  plate.     The  blast  is  regulated  by  a  valve 
(Fig.  76),  which  should  be  as  close  as  possible  to  the  tuyere,  to 
facilitate  the  labors  of  the  workmen.     The  tuyere,  as  before  re- 
marked, is  a  water  tuyere,  which,  after  its  inclination  has  been  de- 


MANUFACTURE    OF   WROUGHT  IRON.  253 

termined,  is  firmly  fastened  in  its  place.  The  nozzle  of  the  blast 
pipe  is  to  be  movable;  it  can  thus  be  dipped  into  the  hearth,  or 
moved  horizontally,  so  as  to  drive  the  blast  towards  any  portion  of 
the  hearth.  The  width  of  the  tuyere  and  the  nozzle  depends  on 
the  quantity  of  metal  melted  at  once ;  but  it  seldom  exceeds  two 
superficial  inches.  The  form  of  the  tuyeres  is  generally  that  of 
a  half  circle  Q  ;  but  sometimes  that  of  a  circle.  The  depth  of  the 
fire-place  varies  according  to  the  quality  of  the  metal  to  be  refined. 
Nine  inches  will  be  sufficient  for  mottled  or  gray  iron  :  but  white 
iron,  of  small  burden,  requires  a  depth  of  ten  or  twelve  inches. 
The  better  the  metal,  the  less  the  depth  of  hearth  required.  A  deep 
hearth  consumes  more  fuel,  and  works  more  slowly,  than  a  shallow 
hearth  ;  but  if  worked  with  proper  attention,  the  product  is  supe- 
rior. Inferior  workmen  require  deep  fires,  as  well  as  hot-short  and 
cold-short  metal.  Shallow  fires  work  fast,  but  require  excellent 
metal,  or  very  expert  workmen  ;  because,  if  anything  goes  wrong 
in  them,  heavy  losses  are  experienced. 

A  number  of  workmen  draw  the  tuyere,  to  a  greater  or  less 
extent,  into  the  hearth.  This  is  productive  of  no  real  benefit. 
Though  by  this  means  we  are  enabled  to  carry  the  blast  a  little 
farther  into  the  fire,  the  advantage  we  derive  from  it  scarcely 
amounts  to  anything.  If  it  is  our  desire  that  the  metal  should  flow 
down,  directly  through  the  current  of  the  blast,  our  object  may  be 
effected  if  the  tuyere  reaches  but  a  short  distance  into  the  coal. 
Besides,  by  drawing  the  tuyere,  its  plate  is  sooner  destroyed  than 
where  the  tuyere  is  close.  We  must  regulate  the  dip  of  the  tuyere 
according  to  the  metal  we  are  smelting.  Gray,  and  hot  or  cold- 
short metal,  and  soft  coal,  require  a  greater  dip  than  good  metal 
and  hard  coal.  Nevertheless,  the  whole  dip  does  not  vary  more 
than  from  7°  to  15°. 

/.  The  manipulation  at  a  blomary  fire  varies  according  to  the 
quality  of  the  metal  with  which  we  have  to  deal.  Therefore,  our 
descriptions  must  be  restricted  to  one  particular  metal,  or  at  least 
to  a  metal  smelted  from  the  same  kind  of  ore.  We  shall  confine 
our  attention  to  gray  or  half  gray  metal,  and  introduce  such  remarks 
occasionally  as  will  indicate  the  method  by  which  other  kinds  of 
metal  are  worked. 

When  the  hearth  is  in  proper  order,  and  when  the  blast  and 
everything  else  are  prepared,  the  interior  of  the  fire-place  is  lined 
with  charcoal  dust,  which  ought  to  be  free  from  sand  and  other 


254  MANUFACTURE   OF  IRON. 

impurities.  The  finer  the  dust,  the  more  serviceable  it  will  be. 
Good  fire  clay  water  thrown  over  it  will,  when  the  whole  mass  is 
well  pounded,  make  it  more  adhesive.  Pieces  of  refractory  ore, 
of  good  quality,  and  even  good  qualities  of  cinder,  are  sometimes 
used  in  lining.  These  materials  are  decidedly  preferable  to  char- 
coal; but  they  require  more  attention  on  the  part  of  the  workmen. 
Coal  is  then  thrown  on,  and  the  fire  kindled.  As  the  fire  rises,  iron 
may  be  melted  down.  The  amount  of  coal,  or  the  size  of  the  heap 
above  the  tuyere,  varies  according  to  the  metal.  A  height  of  from 
twelve  to  eighteen  inches  is  sufficient  for  gray  metal ;  but  for  white 
metal  the  height  of  the  coal  should  be  twenty-four  inches.  When 
the  fire  has  thoroughly  penetrated  the  coal,  the  degree  of  which 
should  be  higher  for  white  than  for  gray  metal,  the  broken  metal 
is  thrown  in  parcels  weighing  from  seventy  to  eighty  pounds  upon 
the  top  of  the  coal  above  the  tuyere.  But  white  metal  is  thrown 
more  from  the  tuyere,  in  case  a  charge  of  more  than  120  pounds  is 
melted  at  once,  which  is  frequently  accomplished  where  the  metal 
is  good,  and  competent  workmen  are  engaged.  Where  the  charges 
are  small,  all  the  metal  is  thrown  on  at  once.  The  blast  is  applied 
moderately;  the  tuyere  is  made  to  dip  very  slightly;  coal  is  con- 
stantly supplied  ;  and  in  case  iron  is  left  to  be  smelted,  it  is  thrown 
on  the  heap.  In  due  time,  the  iron  melts  into  the  bottom  of  the 
fire-place,  and  is  more  or  less  liquid.  If  the  metal  is  gray,  and  if  it 
contains  a  large  amount  of  foreign  matter,  the  process  proves  to  be 
slow,  for  there  are  no  indications  of  solidification.  In  this  case  the 
workman  proceeds  to  increase  the  dip  of  the  tuyere,  to  blow  upon 
the  iron,  and  to  stir  it  repeatedly  by  means  of  iron  bars.  If,  in 
consequence  of  this  manipulation,  the  cinder  increases  on  the  top 
of  the  iron,  it  may  be  let  off,  and  thrown  away,  for  such  cinder  is 
useless.  When  this  is  removed,  the  iron  will  be  exposed  in  a 
greater  degree  to  the  action  of  the  blast.  If  the  metal  still  shows 
no  signs  of  becoming  pasty,  hammer-slag  or  rich  iron  ore  may  be 
thrown  upon  the  fire,  and  melted  down  upon  the  iron.  The  metal, 
when  mottled  iron,  must  be  bad  and  gray  indeed  if  hammer-slag  or 
rich  ore  fails  to  bring  it  to  nature  ;  or  if,  when  it  is  gray  iron,  either 
of  these  fails  to  bring  it  to  a  state  of  boiling.  Iron  and  cinder  will 
then  rise  spontaneously,  and  move  before  the  blast.  The  workmen 
should  take  care  that  no  metal  remains  in  the  corners  of  the  hearth. 
By  degrees,  the  cinder  will  subside,  and  the  iron  will  become  a 
pasty,  tough  mass.  If  it  is  very  hard,  and  feels  like  lead,  the  blast 


MANUFACTURE   OF  WROUGHT  IRON.  255 

is  increased,  for  a  strong  heat  is  required  to  weld  this  tough  mass 
into  a  ball.  By  continually  raising  and  turning  the  iron,  it  will 
become  uniformly  heated.  When  it  becomes  tenacious,  it  may  be 
removed  to  the  hammer  or  squeezer,  and  reduced  to  a  rectangular 
prism,  five  or  six  inches  square  ;  and  if  too  long,  it  may  be  cut  into 
pieces  not  exceeding  in  length  fifteen  or  sixteen  inches.  These 
prisms  form  the  blooms  of  our  markets,  and  are  usually  sent  to  the 
rolling  mills  to  be  transformed  into  bars,  or,  generally,  into  sheet 
iron  or  boiler-plates. 

The  cinder  in  the  hearth,  unless  present  in  too  large  quantity, 
which  is  seldom  the  case,  may  be  suffered  to  remain.  When  the 
scraps  of  iron  are  removed,  and  the  lining  of  the  hearth  secured, 
and,  if  necessary,  repaired,  coal  may  again  be  filled  in,  and  the 
blast  turned  on. 

White  iron,  and  even  mottled  iron,  very  seldom  boil ;  but,  by 
proper  treatment,  arrive  as  a  pasty  mass  at  the  bottom  of  the  hearth. 
This  mass  should  be  broken  up,  and  brought,  to  a  greater  or  less 
extent,  within  the  range  of  the  blast.  But  this  manipulation  requires 
caution,  where  we  have  to  deal  with  white  anthracite  iron  ;  because 
this  metal  commonly  works  too  fast,  and,  if  its  propensity  is  favored, 
bad  iron  results.  Taking  care  to  prevent  the  iron  from  touching 
the  tuyere,  we  should  keep  it  in  a  pasty  state  as  long  as  possible, 
to  afford  the  impurities  an  opportunity  of  combining  with  the  cinder. 
When  the  bottom  of  the  hearth  is  very  cold,  it  is  possible  that  the 
metal  may  be  gray  or  fusible,  though  the  part  which  touches  the 
hearth  may  be  hard  and  cold.  In  this  case,  the  iron,  whether  in 
mass  or  in  pieces,  should  be  carefully  brought  above  the  tuyere, 
and  once  more  melted  down.  In  the  mean  time,  it  is  advisable  to 
discontinue  the  cooling  of  the  bottom  plate. 

g.  The  tools  required  at  the  blomary  fire  are  very  simple.  A  few 
implements  like  crowbars ;  several  pairs  of  tongs  for  lifting  the 
bloom  from  the  fire ;  and  a  couple  of  chisels  shaped  like  hatchets, 
for  cutting  blooms,  are  all  we  require.  Of  the  means  employed  to 
reduce  the  balls  to  a  proper  size,  we  shall  speak  elsewhere. 

7i.  The  results  and  the  expense  of  this  branch  of  iron  manufac- 
ture of  course  vary  greatly.  One  kind  of  metal  will  yield  ninety 
or  ninety- two  per  cent,  of  blooms;  while  another  kind  will  yield  but 
eighty  per  cent.,  or  even  a  less  per  centage  than  that.  The  same 
difference  may  be  observed  in  relation  to  the  quantity  of  fuel  re- 
quired. The  number  of  bushels  of  charcoal  varies  from  150  to 
250  per  ton  of  blooms.  A  blomary  fire,  conducted  night  and  day 


256  MANUFACTURE   OF   IRON. 

for  a  week,  furnishes  from  four  to  seven  tons  of  blooms.  Wages 
of  workmen  from  six  to  seven  dollars  per  ton. 

At  various  places,  hot  blast  is  applied  with  success;  but  at  other 
places,  with  but  little  advantage.  In  most  instances,  it  is  not 
employed. 

In  Europe,  the  varieties  of  blomary  fires,  or  refineries,  are  in- 
numerable. These  varieties  depend,  in  a  greater  or  less  degree, 
on  the  nature  of  the  coal  and  iron  used,  and  upon  the  habits  of  the 
people.  Many  arrangements  produce  better  iron  than  that  we  have 
described.  But  the  advantages  which  these  possess  depend  upon 
circumstances  which  are  not  available  in  the  United  States,  The 
only  ore  which  does  not  follow  the  general  rule  of  the  oxides  and 
hydrates  is  the  magnetic  ore  of  the  different  States.  This  ore  might 
be  made  to  produce  as  good  iron  as  the  best  Swedish.  But  our 
furnace  owners,  in  their  inconsiderate  eagerness  to  realize  every 
possible  advantage,  often  produce  a  metal  whose  quality  cannot  be 
at  all  relied  on.  Our  forge  owners,  therefore,  when  they  desire  a 
good  article,  are  generally  compelled  to  do  the  best  they  can  in 
relation  to  economy  of  fuel. 

IV.  Finery  Fire. 

We  shall  now  describe  a  process  intermediate  between  the  blast 
furnace  and  the  forge  ;  that  is,  the  finery  or  run-out  fire.  A  descrip- 
tion of  this  should  have  followed  that  of  the  blast  furnace ;  but 
as  it  is  of  later  origin,  and  will,  besides,  be  better  understood  after 
the  explanation  of  the  German  finery,  we  thought  it  advisable  to 
delay  our  notice  of  it.  This  invention  is  the  result  of  necessity. 
The  introduction  of  stone  coal,  coke,  and  hot  blast  occasioned  so 
much  bad  pig  iron,  that  some  means  which  should  remove  a  portion 
of  the  impurities  in  the  metal  before  its  removal  to  the  charcoal  forge 
or  to  the  puddling  furnace  were  eagerly  sought.  The  necessity  of 
an  intermediate  process  will  be  readily  admitted  :  but  a  more  awk- 
ward and  unprofitable  invention  than  that  we  are  considering  could 
not  have  originated  from  the  most  unskillful  intellect.  The  appa- 
ratus is  so  worthless  as  scarcely  to  deserve  notice.  In  fact,  when 
we  see  the  large  amount  of  iron  which  is  converted  into  slag  ;  when 
we  see  the  best  charcoal  iron  wasted  by  the  Western  manufacturers, 
we  are  justified,  we  think,  in  wishing  that  the  apparatus  had  never 
been  invented.  But  the  invention  exists,  and  there  is  no  imme- 
diate prospect  of  getting  rid  of  it ;  therefore  it  is  our  duty  to  re- 
cord its  existence,  and  to  exhibit  its  construction. 


MANUFACTURE   OF  WROUGHT   IRON.  257 

Fig.  78  represents  a  vertical  section,  and  Fig.  79  a  ground-plan, 
of  a  finery.  It  is  erected  on  a  platform  of  brick,  about  twenty 
inches  in  height,  in  the  middle  of  which  is  the  hearth  or  fire-place 
A.  At  each  of  the  four  corners  an  iron  column  is  erected,  upon 

Fig.  78, 


Finery,  or  run-out  fire. 

'which  a  brick  chimney,  two  feet  in  width  inside,  is  built.  This 
fire  generally  works  with  four  tuyeres,  that  is,  two  on  opposite 
sides;  or  with  four  nozzles,  and  but  two  tuyeres,  on  the  same  side. 
When  the  latter  is  the  case,  two  currents  of  blast  are  conducted  into 
each  tuyere,  that  the  whole  surface  of  the  melted  metal  may  be  ex- 
posed to  the  action  of  the  blast.  The  sides  of  the  hearth  are  formed 
of  hollow  cast  iron  plates,  through  which  a  current  of  cold  water 
is  constantly  running,  to  prevent  their  melting.  The  hearth  is  gene- 
rally from  three  to  three  and  a  half  feet  in  length,  twenty-four  inches 
in  width,  and  twenty-four  or  thirty  inches  in  depth.  Around  the  fire 
are  sheet  iron  doors,  fastened  to  the  columns;  these  are  alternately 
used  to  prevent  the  disturbance  occasioned  by  strong  draughts  of 
wind.  Such  fires  produce  a  great  deal  of  dust,  heat,  and  rubbish, 
17 


258  MANUFACTURE   OF  IRON. 

and  are  generally  removed  from  the  main  buildings.  The  bottom 
of  the  hearth  is  formed  of  coarse  sand,  and  often  of  coke  dust.  The 
nozzles  a  a  are  from  an  inch  to  an  inch  and  a  quarter  wide.  The 
blast,  of  which  about  400  cubic  feet  per  minute  are  required,  is  pro- 
Fig.  79. 


Ground-plan  of  a  finery. 

duced  in  iron  cylinders.  In  a  prolongation  of  the  tapping  hole 
5,  is  the  chill  mould ;  this  is  a  heavy,  cast  iron  trough,  sufficiently 
large  to  receive  the  contents  of  the  hearth.  It  is  commonly  ten 
feet  in  length,  thirty  inches  in  width,  and  four  inches  in  depth. 
A  current  of  water  is  led  around  it  to  keep  it  cool.  Pipes,  suffi- 
ciently large  for  throwing  a  strong  current  of  water  upon  the  hot 
iron,  should  be  at  our  disposal  at  all  times. 

When  the  hearth  is  ready  for  operation,  fire  may  be  placed  on  it, 
and  coke,  or,  as  in  many  instances,  charcoal  thrown  on ;  the  blast 
is  then  applied,  and  pig  iron,  to  the  amount  of  five  or  six  hundred 
pounds,  charged  at  once.  If  the  iron  is  very  gray,  a  greater  dip 


MANUFACTURE   OF   WROUGHT  IRON.  259 

of  the  nozzles  and  of  the  tuyere  is  given ;  this  secures  stronger 
blast  upon  the  metal,  which,  after  being  charged,  soon  comes  down. 
When  the  iron  disappears  from  the  top,  another  charge  is  given, 
and  melted  down,  care  being  taken  that  the  coke  is  duly  supplied. 
In  this  way,  twenty  pigs,  or  generally  one  ton  of  iron,  are  melted, 
^ome  time  is  required,  where  the  iron  is  gray,  before  the  metal  can 
be  let  out ;  and  when  sparks  of  burning  iron  appear  to  be  thrown 
off  from  the  top  of  the  coke,  this  time  is  supposed  by  the  workmen 
to  have  arrived.  After  the  lapse  of  about  two  hours,  the  time  re- 
quired for  one  heat,  the  tapping  hole  is  opened,  and  the  iron  runs 
into  the  chill  mould,  or,  as  it  is  called  by  the  workmen,  the  pit.  This 
mould  has  been  previously  washed  with  a  thin  clay  solution,  to  pre- 
vent adhesion  of  the  refined  metal  to  its  surface.  Cinder  also  flows 
off  with  the  iron.  As  soon  as  the  metal  becomes  solid,  a  strong  cur- 
rent of  cold  water  is  permitted  to  flow  upon  it,  the  reason  for  which 
we  shall  explain  in  another  place.  In  the  mean  while,  fresh  coke 
and  pig  iron  are  charged,  and  the  process  continued  as  before. 

a.  The  quality  of  the  refined  iron  depends  principally  upon  that 
of  the  pig  metal ;  while  the  quality  of  the  latter  depends  upon  the 
previous  manipulation  in  the  blast  furnace.  Good  soft  gray  or 
white  iron  generally  furnishes  metal  of  excellent  quality ;  but  white, 
hard,  and  brittle  pig  is  very  little  improved  in  the  finery.  There 
have  been  cases  in  which  2300  pounds  of  pig  produced  a  ton  of 
metal ;  and  we  have  known  instances  in  which  3000  pounds  of 
coke  iron  were  used  to  produce  the  same  amount.  It  is  beyond 
human  skill  to  suggest  any  method  by  which  a  waste  of  iron,  to  a 
greater  or  less  degree,  can  be  prevented. 

To  what  extent  this  kind  of  work  answers  its  purpose  as  a  fore- 
runner of  the  finery  forge  and  puddling  furnace,  we  shall  investi- 
gate at  the  close  of  this  chapter.  Some  years  since,  Mr.  Detmold, 
of  New  York,  introduced  an  improvement  upon  this  mode  of  refining. 
He  constructed  a  reverberatory  furnace,  resembling  in  form  the 
puddling  furnace.  The  pig  iron  was  melted  on  a  large  hearth,  and 
the  blast  thrown  upon  its  surface  to  whiten  it.  But  there  is  little 
merit  in  either  of  these  refineries. 

V.  Puddling  Furnaces. 

The  reverberatory  or  puddling  furnace  is,  unquestionably,  of  all 
arrangements,  the  best  adapted  to  convert  cast  iron  into  bar  iron. 
The  imperfect  results  which  have  hitherto  been  obtained  with  re- 
spect to  the  quality  of  iron,  have,  as  might  have  been  expected, 


260 


MANUFACTURE   OF   IRON. 


depended  upon  a  variety  of  circumstances.  We  shall  endeavor  to 
give  a  clear  and  comprehensive  insight  into  the  whole  manipulation, 
practically  and  theoretically ;  for  we  consider  this  the  most  import- 
ant subject  in  our  treatise.  How  far  we  shall  succeed  in  our  in- 
tentions, the  intelligent  reader  will,  of  course,  be  most  competent 
to  judge. 

An  historical  sketch  of  this  branch  of  the  iron  manufacture  would 
require  more  space  than  we  can  spare.  It  would,  besides,  be  of 
little  interest  to  show  in  what  manner  the  puddling  process  is  per- 
formed on  a  sand  bottom,  or  even  on  a  bottom  of  coke  dust.  We 
shall,  therefore,  simply  describe  the  process  of  the  present  day ; 
and,  while  we  shall  principally  dwell  upon  the  arrangements  em- 
ployed in  the  United  States,  we  shall  notice  some  of  the  most  in- 
teresting ones  in  Europe. 

a.  At  Pittsburgh,  and  throughout  the  West,  the  single  furnace, 
and  on  the  eastern  side  of  the  Alleghany  Mountains  the  double 
furnace,  are  generally  employed.  The  former  is  the  most  an- 
cient form  of  the  puddling  furnace,  and  for  this  reason  is  probably 
generally  used  in  the  Western  States.  Fig.  80  exhibits  a  side  ele- 

Fig.  80. 


Elevation  of  a  puddling  furnace. 


MANUFACTURE   OF  WROUGHT  IRON.  261 

vation  of  such  a  furnace,  including  the  stack.  It  represents  the 
work  side  at  that  point  of  view  from  which  the  door  to  the  interior 
can  be  seen.  The  stack,  or  chimney,  is  generally  from  thirty  to  forty 
feet  in  height,  and  erected  upon  a  solid  foundation  of  stones ;  this 
foundation  is  covered  with  four,  or,  in  many  cases,  with  but  two  cast 
iron  plates ;  upon  these  plates,  four  columns  of  cast  iron  are  erected, 
forming  four  corners  of  the  chimney.  A  square  frame,  formed  of 
four  cast  iron  plates,  is  laid  upon  these  columns  ;  and  upon  this 
frame  the  chimney  is  erected.  The  exterior  or  rough  wall  of  the 
chimney,  width  nine  inches,  is  made  of  common  brick,  and  well 
secured  by  iron  binders,  which  are  generally  flat  hoops,  from  one- 
eighth  to  three-sixteenths  of  an  inch  thick.  These  hoops  occupy 
no  more  space  than  a  layer  of  mortar  ;  and  they  should  be  placed 
at  intervals  of  two  or  three  feet,  or  sometimes  of  even  three  or 
four  feet,  while  laying  the  brick.  The  binders,  into  which  an  ob- 
long hole  should  be  made,  should  overlap  the  brick  about  two 
and  a  half  inches;  through  this  hole  a  bar  three-fourths  of  an  inch 
square  may  be  pushed.  Two  of  these  upright  bars,  which  should 
extend  the  whole  height  of  the  stack,  are  required  at  each  corner. 
The  top  of  the  chimney  is  covered  with  a  cast  iron  plate  ;  but 
this  is  sometimes  dispensed  with.  Such  a  top-plate  is  a  useful 
appendage,  for  it  secures  the  bricks:  but,  if  not  properly  made,  it  is 
troublesome ;  it  is  apt  to  break  into  halves,  and  fall  down,  under 
the  influence  of  heat.  To  prevent  this  accident,  it  is  advisable  that 
the  top-plate  should  be  formed  of  four  pieces  screwed  together ; 
the  points  in  the  corners  should  be  left  open,  to  give  room  for  ex- 
pansion from  the  centre  of  the  plate.  Fig.  81  represents  such  a 
plate  from  above,  and  Fig.  82  in  a  ver- 
tical section,  with  a  portion  of  the  brick 
work  of  the  chimney.  The  interior  of 
the  stack  should  be  built  of  good  fire 
brick;  for  single  furnaces  sixteen,  and 
for  double  furnaces  from  eighteen  to 
twenty,  inches  square.  The  frequent 
expansion  and  contraction  of  this  lining 
under  a  high  heat  affect  its  durability. 
A  space  of  an  inch  or  an  inch  and  a 
half,  left  between  the  rough  wall  and  the  Plan  of  a  chimney  lop< 

in-wall,  with  a  brick   occasionally  pro- 
jecting, will,  to  a  great  degree,  prevent  contraction.     Fig.  82  ex- 
hibits the  arrangement  of  the  in-wall  and  rough  wall  distinctly.    A 


262 


MANUFACTURE   OF   IRON. 


•wire  reaches  from  the  damper  on  the  top  to  the  side  of  the  furnace  , 
the  most  convenient  place  for  the  workmen. 

Fig.  82. 


Fig.  83. 


Chimney  top. 

I.  The  exterior  of  the  furnace,  eleven  or  twelve  feet  in  length, 
and  about  five  feet  in  height,  is  composed  of  cast  iron  plates. 
Into  the  small  square  hole,  coal  is  thrown.  The  large  one  is  a 
sliding  door  for  the  charge  and  discharge  of  the  iron ;  the  hole  in 
this  door  is  designed  for  the  introduction  of  the  tools.  The  door 
is  suspended  on  a  chain,  fastened  to  a  lever,  which  is  above  the 

head  of  the  workman.  Fig.  83  re- 
presents the  door  on  a  large  scale, 
in  which  a  front  view,  a  vertical 
and  horizontal  section,  are  shown. 
The  average  size  of  this  door  is 
twenty-two  inches  in  width,  and 
twenty-seven  inches  in  height.  Its 
inside  towards  the  fire  is  filled  with 
fire  brick,  tightly  wedged  in.  The 
square  work  hole  is  very  much 
sloped  inside,  to  enable  the  work- 
man to  reach  every  part  of  the 
furnace  hearth. 

Fig.  84  exhibits  a  vertical  sec- 
tion of  the  furnace  and  the  stack.  The  whole  arrangement  is  a 
judicious  one.  The  structure  is  built  of  fire  brick  and  common 
brick  ;  the  former  is  indicated  by  the  lighter,  and  the  latter  by  the 


Door  of  a  puddling  furnace. 


MANUFACTURE  OF  WROUGHT   IRON.  263 

darker,  shade  of  lining.  The  fire-place  is  a  separate  chamber,  de- 
signed for  nothing  else  than  the  combustion  of  fuel.  Behind  the 
fire-place  is  the  hearth,  where  the  iron  is  charged,  melted,  and 
puddled.  The  hearth  is  heated  in  part  directly  bj  the  flame,  but 

Fig.  84. 


Vertical  section  of  a  puddling  furnace. 

chiefly  indirectly  by  the  reflected  heat  from  the  roof,  for  which 
reason  this  furnace  is  called  a  reverberatory  furnace.  For  western 
bituminous  coal,  a  grate  measuring  three  by  two  feet  is  sufficiently 
large;  but  for  anthracite  coal,  a  much  larger  grate  is  required.  The 
hearth  is  five  feet,  sometimes  six  feet  in  length,  and  three  and  a 
half  or  four  feet  in  width,  and  of  an  irregular  form.  Its  bottom 
and  sides  are  made  of  cast  iron,  and  prevented  from  melting  by  a 
constant  current  of  cold  air.  Where  this  is  not  sufficiently  strong, 
a  dish  of  water  is  sometimes  thrown  under  the  bottom.  By  care  on 
the  part  of  the  workman,  the  application  of  water  is  unneces- 
sary. If  the  bottom  plates  are  so  thin  as  to  be  in  danger  of  bend- 
ing, they  should  be  supported  by  props  made  of  iron  rods. 


264 


MANUFACTURE   OF  IRON. 


After  heating  the  hearth,  the  flame  is  conducted  through  the 
inclined  flue  into  the  stack.  The  size  of  the  flue  depends  on  that 
of  the  hearth,  and  upon  the  interior  dimensions  and  height  of  the 
stack.  A  flue  ten  by  twelve  inches  square  is  considered  to  be 
sufficiently  large  for  a  single  furnace.  A  large  hearth  with  a  narrow 
and  low  stack  requires  a  larger  flue  than  a  small  hearth  with  a 
high  or  wide  chimney.  The  dimensions  of  the  grate  increase  with 
the  incombustible,  and  decrease  with  the  inflammable,  nature  of  the 
fuel  we  employ.  A  grate  measuring  one  square  foot  is  large  enough 
for  dry  wood ;  while  for  anthracite  coal  a  grate  of  twenty  square  feet 
is  required.  Behind  the  furnace,  on  one  side  of  the  stack,  a  small 
fire  is  seen  burning.  This  fire  is  to  be  kept  up  at  those  furnaces  where 
the  fire  bricks  produce  cinders,  or  where  the  slag  from  the  furnace 
hearth  passes  the  flue  bridge.  The  accumulation  of  cinder  obstructs 
the  passage  of  the  flame;  and  a  small  fire  at  the  flue,  with  a  slight 
draught  into  the  chimney,  keeps  that  part  of  the  furnace  sufficiently 
warm  to  prevent  such  accidents.  Fig.  85  represents  a  section  of  a 

Fig.  85. 


Vertical  section  of  a  single  puddling  furnace. 

furnace  on  a  larger  scale  than  the  above ;  the  furnace  also  is  shown 
more  distinctly.  The  ground-plan  of  this  furnace  is  exhibited  by 
Fig.  86,  in  which  the  form  of  the  hearth,  the  plan  of  the  fire  cham- 
ber, grate,  and  the  fire  bridge,  are  clearly  shown.  In  these  illus- 
trations, the  cast  iron  plates  which  enclose  the  hearth  are  also  clearly 


MANUFACTURE   OF  WROUGHT  IRON.  265 

shown.     These  plates,  about  ten  or  twelve  inches  high,  are  made  to 
cross  the  bridges,  as  well  as  to  secure  whatever  else  needs  c  ;?uri 

Fig.  86. 


Ground  plan  of  a  single  puddling  furnace. 

c.  At  Pittsburgh,  and  at  most  of  the  Western  Works,  charcoal 
iron  is  exclusively  used  in  the  puddling  forges.     The  process  con- 
sists of  puddling  and  boiling.     Puddling  is  very  nearly  the  same 
thing  as  boiling,  with  slight  differences  in  manipulation.     In  pud- 
dling, metal  from  the  run-out  fire  is  worked,  and  sometimes  mixed 
with  good  white  charcoal  metal  from  the  blast  furnace.    In  boiling, 
the  gray  or  mottled  pig  iron  is  brought  directly  to  the  furnace,  and 
refined  by  means  of  slag;  this  iron,  in  the  course  of  the  manipula- 
tion, rises  along  with  the  cinder,  and  its  motion  is  like  that  of  boil- 
ing water.     The  latter  process  would,  of  course,  be  the  more  pro- 
fitable, if  generally  effected ;  but  on  account  of  cinder,  there  is  a 
limit  to  the  boiling  operation.     Therefore,  in  a  rolling  mill  forge, 
half  the  furnaces  are  employed  for  boiling,  and  half  for  puddling ; 
the  latter  supplies  cinder  for  the  former. 

d.  The  process  of  operation,  in  these  furnaces,  is  as  follows:  A 
new  furnace  is  dried  slowly ;  that  is,  a  small  fire  is  put  in  the  grate, 
not  quite  filled  with  coal.     This  fire  is  usually  kept  up  for  three  or 
four  days.     After  the  furnace  is  dry,  which  is  indicated  by  the  ces- 
sation of  vapors  from  the  brick  work,  the  grate  is  cleared  from  clink- 
ers.    A  good  stone  coal  fire  is  then  kindled,  which,  in  the  course 
of  four  or  five  hours,  will  bring  the  furnace  to  a  heat  proper  for 
charging  the  metal.    Previous  to  this,  the  iron  bottom  of  the  hearth 
is  covered  with  finely  pounded  cinders  from  a  charcoal  forge,  or  from 
another  puddling  furnace,  or  from  a  re-heating  furnace.     If  none 
can  be  obtained,  cinder  from  a  blast  furnace  will  answer.     This 
cinder  is  broken  into  uniform  pieces  of  about  an  inch  in  size.     A 


266  MANUFACTURE   OF   IRON. 

portion  of  it  is  thrown  around  the  sides  and  bridges,  and  covers  the 
bottom  to  the  height  of  three  or  four  inches.  Fire  should  then  be 
applied  to  the  cinder  for  about  five  hours.  By  pounding  it,  when 
it  gets  soft,  so  as  to  fill  all  the  crevices,  the  cinder  will  not  only  melt 
more  readily,  but  the  furnace  will  become  more  thoroughly  heated. 
A  perfect  fusion  of  the  cinder  is  required  before  iron  is  charged ; 
otherwise,  it  will  not  form  a  solid  lining  over  the  iron  plates  and 
bottom.  But  for  this  object  alone  it  is  employed.  If  crevices  are 
left  in  the  cinder,  drops  of  melted  iron  will  find  them,  and  penetrate 
to  the  iron  bottom  of  the  hearth.  Thus  the  thickness  of  the  bottom 
is  not  only  unnecessarily  increased,  but  it  is  made  rough,  and  occa- 
sions troublesome  manipulation ;  besides,  a  portion  of  the  iron  is 
lost.  When  the  cinder  is  melted,  and  the  bottom  and  sides  pro- 
perly protected,  the  door  is  lifted,  and  cold  cinder  mixed  with  the 
melted  mass.  When  the  bottom  is  so  far  cooled  that  the  tools 
make  no  impression  on  it,  the  metal  is  thrown  in,  the  door  shut, 
and  the  fire  brought  to  good  order.  The  door,  which,  as  shown  in 
the  drawing,  moves  in  a  frame,  is  fastened  by  two  wedges,  one  on* 
each  side.  These  wedges  are  driven  in  between  the  frame  and  the 
door;  for  which  reason,  the  door  is  about  an  inch  smaller  than  the 
frame.  Fine  cinder,  or  hammer-slag,  is  thrown  around  the  door, 
to  prevent  a  draught  of  cool  air  through  the  crevices.  In  the  work 
hole  a  piece  of  coal  is  laid,  covered  by  a  small  plate  of  sheet  iron. 
Meanwhile  the  door  is  secured  by  the  puddler,  and  the  helper 
charges  coal,  cleans  the  grate,  and  heats  the  furnace  as  strongly 
as  possible.  Within  a  quarter  of  an  hour,  the  iron,  in  some  places, 
begins  to  get  red ;  the  helper  then  takes  a  bar,  and  turns  the  iron, 
that  is,  he  moves  the  warm  iron  to  a  cold,  and  the  cold  iron  to  a 
warm  place;  after  which,  a  fresh  charge  of  coal  is  supplied. 
Within  half  an  hour,  if  everything  is  in  good  order,  the  metal  be- 
comes white,  and  ready  to  melt,  when  the  helper,  by  means  of  a 
hook,  breaks  the  pieces,  and  mixes  the  iron  with  the  half  liquid 
cinder ;  at  the  same  time,  the  puddler  stirs  the  grate,  with  the  ob- 
ject of  augmenting  the  heat.  In  forty-five  minutes  the  iron  may 
be  brought  under  the  protection  of  the  cinder.  At  this  point,  the 
divergence  in  the  manipulations  of  puddling  and  boiling  com- 
mences. We  shall  first  speak  of  puddling;  but,  preliminary  to 
this,  we  shall  describe  the  tools  applicable  to  this  process. 

e.  Most  of  the  tools  consist  of  iron  bars  and  hooks.  Five  or  six 
are  required  at  each  furnace.  Fig.  87  represents  a  bar  from  five 
to  six  feet  in  length.  One  end  of  it  is  sharpened  and  square ;  the 


MANUFACTURE   OF  WROUGHT  IRON.  267 

other  end  terminates  in  a  round  knob,  which  enables  the  workman 
to  handle  it  with  facility.     The  lengthier  portion  of  the  ba-'ai*." 

Fig.  87. 


Puddling  bar. 

hook  is  eight-sided,  for  a  bar  of  this  shape  is  held  more  firmly  than 
one  that  is  round.     These  tools  suffer  greatly  from  the  heat  of  the 

Fig.  88. 


Puddling  hook. 

furnace,  particularly  when  used  for  too  long  a  time  at  once  by  care- 
less workmen.  The  heat  is  apt  to  slit  and  break  the  iron.  For 
this  reason,  charcoal  forge  iron  is  preferable  to  puddled  iron  for 
tools.  A  water  trough,  six  feet  in  length,  twelve  inches  in  depth, 
and  fifteen  inches  in  width,  is  attached  to  each  furnace.  This 
trough  should  be  constantly  supplied  by  a  stream  of  cold  water,  to 
cool  the  heated  tools.  A  large  pair  of  tongs  is  also  required  to 
grasp  the  hot  balls  in  the  furnace.  These  balls  are  either  dragged 
on  iron  slopes  to  the  hammer  or  squeezer,  or,  as  is  more  commonly 
the  case,  they  are  loaded  on  iron  wheelbarrows  made  expressly  for 
the  purpose,  and  wheeled  by  the  helper  to  their  appropriate  desti- 
nation. A  flat  bar,  with  a  round  handle,  for  stirring  the  fire,  and 
cleaning  the  grate  ;  a  coal  shovel;  a  small  hammer ;  and  an  oblong, 
sheet  iron  dish  for  throwing  water  or  hammer-slag  in  the  furnace, 
complete  the  list  of  implements  requisite  at  a  puddling  furnace. 
/.  When  the  metal  is  heated  to  such  a  degree  that  a  blow  from  a 
hook  will  break  it,  the  damper  should  be  lowered.  If  the  iron  is 
not  of  the  best  quality,  the  damper  should  be  very  nearly  closed, 
so  as  to  prevent  the  access  of  oxygen  until  the  metal  is  thoroughly 
mixed  with  the  cinder.  By  this  means,  the  iron  is  protected,  time 
is  given  to  the  workman  to  break  it,  and  an  opportunity  afford- 
ed for  a  combination  of  the  impurities  with  the  cinder.  Where 
the  metal  is  of  good  quality,  so  much  attention  is  not  required  at 
this  stage  of  the  process.  When  the  iron  is  well  worked  into  the 
cinder,  the  damper  may  be  slightly  raised ;  and  if  but  little  flamo 


268  MANUFACTURE    OF  IRON. 

is  in  the  furnace,  a  small  quantity  of  coal  may  be  thrown  into  the 
grate,  and  the  fire  stirred.  At  this  point,  the  duties  of  the  assistant 
workman  cease.  The  puddler,  then,  with  a  good  sharp  bar,  frees 
the  bottom  and  sides  of  the  furnace  of  any  lumps  of  metal,  or 
lumps  of  iron  already  refined ;  and  in  case  the  bottom  is  not  per- 
fectly smooth,  he  takes  away  the  projecting  parts,  which  are  gene- 
rally metal,  adhering  to  the  cinder.  Gradually  the  mixture  of  iron 
and  cinder  rises  spontaneously,  and  exhibits  a  kind  of  fermentation. 
This  may  be  kept  down  by  raising  the  damper;  or,  by  stirring  the 
fire,  it  may  be  permitted  to  rise  still  higher.  If  all  the  iron  is 
melted,  and  the  furnace  in  good  order,  the  rising  must  be  prevented  ; 
but  if  the  furnace  is  not  quite  clean,  it  is  preferable  to  maintain  a 
low  temperature  until  all  the  iron  is  mixed  in  small  particles  with 
the  cinder.  When  this  is  fairly  accomplished,  the  damper  may  be 
slightly  raised,  so  that,  in  addition  to  the  heat,  a  small  quantity  of 
oxygen  may  pass  through  the  iron.  Should  the  metal  have  been  of 
good  quality,  but  little  time  is  required  to  separate  the  iron  and 
cinder ;  this  stage  of  the  operation  is  called  coming  to  nature,  and 
is  characterized  by  the  iron  forming  at  first  small,  and  to  all  appear- 
ances round  particles  of  the  size  of  peas,  which  swim  in  the  cinder. 
When  these  particles  of  refined  iron  begin  to  grow  larger,  by  ad- 
hering one  to  another,  the  damper  may  be  raised,  and  the  heat 
in  the  furnace  brought,  by  degrees,  to  the  highest  point.  The 
accumulation  of  the  particles  then  proceeds  rapidly.  Active  mani- 
pulation is  required  to  prevent  the  formation  of  too  large  masses. 
By  breaking  up,  and  turning,  the  whole  mass  is  uniformly  heated. 
After  a  short  time,  by  squeezing  the  small  lumps,  by  means  of  the 
bar  or  hook,  round  balls,  twelve  or  fifteen  inches  in  diameter,  or 
seventy  or  eighty  pounds  in  weight,  are  formed.  After  all  the  balls 
are  finished,  the  work  hole  is  shut  for  a  few  minutes,  that  a  final  and 
thorough  heat  may  be  given  to  the  iron.  When  this  is  accomplished, 
the  wedges  at  the  door  are  loosened,  the  door  is  lifted  by  the  helper, 
and  the  puddler  takes  one  ball  after  another  to  the  hammer  or 
squeezer,  or  loads  it  on  an  iron  hand-cart,  which  the  helper  wheels 
to  its  place  of  destination. 

g.  If  the  metal  charged  is  gray  or  mottled,  a  somewhat  different 
method  of  working  it  is  pursued.  So  far  as  the  heating  of  the  iron 
is  concerned,  but  little  difference  in  the  treatment  is  required,  though 
the  heat,  before  commencing  operations,  must  be  stronger  than  in 
the  puddling  process.  It  requires  some  skill  to  hit  the  proper  time 
for  commencing  operations.  If  we  commence  too  soon,  the  iron  will 


MANUFACTURE    OF   WROUGHT  IRON.  269 

divide  into  small  particles,  and  assume  a  somewhat  sandy  appear- 
ance; in  this  case,  the  work  will  not  only  proceed  slowly,  but  the 
iron  will  be  of  inferior  quality.  If,  on  the  other  hand,  the  metal  is 
melted  perfectly,  the  result  will  be  rapid  work,  and  an  excellent 
quality  of  iron.  Melting  of  the  metal  may  be  accomplished  by 
leaving  the  damper  open  until  the  iron  and  cinder  have  become 
sufficiently  liquid,  after  which  it  must  be  shut  to  exclude  atmo- 
spheric air.  At  this  time  the  interior  of  the  furnace  appears  dark 
and  smoky,  and  black  fumes  issue  from  the  almost  closed  top  of  the 
stack.  The  melted  mass  is  continually  stirred,  and  at  intervals  of 
a  few  minutes,  fluxes,  consisting  of  hammer-slag,  or  pounded  ore 
and  water,  are  applied.  If  these  act  their  part  well,  the  surface  of 
the  mass  will  be  covered,  to  a  greater  or  less  extent,  with  blue 
flames.  Within  twenty  minutes,  the  cinder  commences  to  rise;  a 
kind  of  fermentation  takes  place  beneath  its  surface;  and  the  mass, 
at  first  but  two  inches  high,  rises  to  a  height  of  ten  or  twelve  inches. 
Whilst  the  cinder  and  iron  are  thus  rising,  constant  stirring  is 
required,  to  prevent  the  settling  of  the  iron  on  the  bottom,  which  is 
now  deprived  of  the  direct  influence  of  heat.  If  the  process  goes 
on  well,  no  iron  is  yet  visible.  When  the  cinder  rises  to  its  proper 
height,  the  duties  of  the  helper  cease.  The  puddler  then  com- 
mences, by  means  of  a  sharp  bar,  to  free  the  bottom  and  sides  of 
the  furnace  of  lumps  of  metal.  At  this  point  the  damper  may  be 
slightly  raised;  and,  by  the  addition  of  a  small  quantity  of  coal,  a 
bright  flame  may  be  produced.  Soon  after  this,  the  iron  is  seen  in 
small,  bright  spots  at  the  surface  of  the  cinder,  and  then  alternately 
appears  and  disappears.  Brisk  stirring  at  the  bottom  and  at  the 
sides  is  now  requisite  to  prevent  the  iron  from  remaining  at  the 
cold  bottom,  after  having  once  been  at  the  surface.  The  iron  and 
cinder,  when  in  lively  motion,  have  a  striking  resemblance  to  the 
boiling  of  corn;  from  this  resemblance  the  term  lolling  is  derived. 
At  a  well-managed  furnace,  the  boiling  lasts  about  a  quarter  of  an 
hour;  the  cinder  gradually  sinks;  and  the  iron  appears  in  the  form 
of  porous,  spongy  masses,  of  irregular  size,  which  are  to  be  stirred, 
to  prevent  their  adhering  together  in  lumps  too  large  to  be  formed 
into  balls.  At  this  stage  of  the  process,  the  heat  should  be  raised 
as  high  as  practicable.  The  iron,  even  in  its  spongy  form,  will  be 
quite  hard,  and  a  good  heat  is  required  to  soften  it  sufficiently  for 
welding.  If  the  heat  is  not  strong,  the  iron  is  not  apt  to  stick;  and 
if  put  together  by  squeezing,  it  will  not  bear  shingling ;  besides,  the 
balls  are  likely  to  break  under  the  hammer,  or  in  the  squeezer. 


270  MANUFACTURE   OF  IRON. 

The  method  of  removing  the  balls  is  the  same  as  that  before  de- 
scribed. 

Puddling  and  boiling  differ  mainly  in  the  method  of  bringing  the 
iron  to  nature ;  that  is,  producing  that  transformation  of  metal  which 
constitutes  bar  iron.  The  difference  between  white  and  gray  iron 
does  not  produce  the  difference  in  the  work,  but  the  degree  of  fusi- 
bility of  the  iron,  and  the  time  required  to  crystallize  it.  The  de- 
scription we  have  given  of  boiling  and  puddling  applies  only  to 
cases  in  which  good  wrought  iron  is  produced.  Instances  occur 
in  which  both  processes  are  applied  in  the  same  case;  and  we 
think  we  shall  but  slightly  err  if  we  state  that  the  puddling  opera- 
tion is  generally  conducted,  to  a  greater  or  less  degree,  to  a  state 
of  boiling. 

h.  The  construction  of  boiling  and  puddling  furnaces  does  not 
vary  materially  except  in  the  depth  of  the  hearth ;  that  is,  in  the 
distance  from  the  work-plate  below  the  door  to  the  bottom  plate. 
In  the  latter,  a  depth  of  six  inches  is  sufficient ;  while  in  the  former, 
a  depth  of  eleven  or  twelve  inches  is  required.  In  the  puddling 
furnace,  the  distance  between  the  bottom  and  top  seldom  exceeds 
twenty  inches ;  in  the  boiling  furnace,  it  varies  from  twenty  to  thirty 
inches.  In  the  former,  the  iron  boshes  do  not  always  reach  all 
round  the  hearth,  but  are  frequently  confined  to  both  bridges ;  in 
addition  to  which,  the  sloping  sides  are  of  fire  brick. 

i.  In  puddling,  the  furnace  is  charged  with  metal  alone;  but  in 
boiling,  cinder  is  charged  along  with  the  metal.  When  the  balls 
are  removed  from  the  boiling  furnace,  a  large  mass  of  fused  cinder 
remains  in  the  bottom,  a  part  of  which  is  let  off,  through  the  tap- 
hole  below  the  work  door,  into  a  two-wheeled  iron  hand-cart.  A 
small  portion  of  the  liquid  cinder  is  left  in  the  furnace.  A  large 
quantity  of  cold  cinder,  from  the  hammer  or  squeezer,  is  now 
thrown  upon  the  pasty  cinder;  and  upon  this  cinder  the  pig  metal 
is  placed.  The  cinder  which  results  from  boiling  is  of  inferior 
quality,  but  it  is  improved  when  mixed  with  that  from  the  pud- 
dling furnace.  For  this  reason,  puddling  furnaces  are  used  at  the 
western  puddling  establishments.  Charcoal  forge  cinder,  added  to 
the  above  hammer  cinder,  is  still  better  than  that  from  the  puddling 
furnace. 

At  the  Pittsburgh  works,  it  is  customary  for  the  puddlers  to  make 
six,  and  the  boilers  to  make  five  heats  in  a  turn,  of  a  charge  weigh- 
ing 350  pounds.  This  is  accomplished  in  eight  or  nine  hours.  The 


MANUFACTURE   OF   WROUGHT   IRON. 


271 


workmen  make  but  two  turns  in  twenty-four  hours ;  therefore  an 
interval  of  from  six  to  seven  hours,  during  the  night,  is  left,  in 
which  the  furnaces  are  stopped  up.  The  workmen  change  every 
day  at  twelve  o'clock ;  the  first  set  begin  at  three  or  four  o'clock 
in  the  morning,  and  the  second  cease  at  about  ten  at  night. 

Jc.  The  construction  of  the  western  puddling  furnaces  does  not 
differ  materially  from  that  of  the  single  furnace  generally  in  use 
in  England  ;  but  they  are  distinguished  by  iron  boshes,  by  which 
the  hearth  is  lined  all  round,  which  is  not  the  case  anywhere  else 
in  single  furnaces. 

In  the  Eastern  States,  there  are  scarcely  any  single  puddling 
furnaces  in  use.  Where  anthracite  is  employed,  the  construction 
of  the  fire-places  is  modified.  The  following  illustrations  will 
serve  the  purpose  of  description  :  Fig.  89  represents  an  anthracite 
furnace  dissected  vertically  through  the  grate,  hearth,  and  chimney. 
The  arrangement  varies  but  slightly  from  that  of  the  single  furnace 
we  have  already  described,  with  the  exception  that  the  grate  is  deep- 
er. In  this  furnace,  coal  can  be  filled  to  the  depth  of  from  twenty  to 
twenty-four  inches ;  while,  in  the  bituminous  coal  furnace,  a  depth 

Fig.  89. 


ce, 


Puddling  furnace  for  anthracite  coal. 

of  ten  or  twelve  inches  is  sufficient.  The  cross  binders,  which  we 
omitted  to  mention  in  our  description  of  the  single  furnace,  are 
marked  a  a.  These  binders  are  a  necessary  element  in  the  con- 
struction of  a  furnace.  They  are  wrought  iron  square  bars,  either 
with  screw  and  nut,  or  with  a  key,  and  serve  to  bind  together  the 
cast  iron  plates  of  the  enclosure.  They  prevent  the  sinking  of  the 
roof  caused  by  the  expansion  and  contraction  of  the  fire  brick. 


272  MANUFACTURE   OF  IRON. 

The  two  holes  below  the  grate  serve  for  the  passage  of  the  blast. 
For  this  purpose,  one  orifice  is  usually  deemed  sufficient.  The 
blast  machines  are  fans  ;  and,  as  pressure  of  the  blast  is  unneces- 
sary, they  serve  every  purpose.  We  shall  speak  of  these  in  another 
chapter. 

The  incombustibility  of  anthracite  coal  makes  the  application  of 
blast  necessary.  A  chimney  cannot  draw  through  a  high  column 
of  coal  an  amount  of  air  sufficient  to  give  it  the  requisite  heat.  If 
the  column  of  coal  in  the  grate  is  left  low,  all  of  the  oxygen  of  the 
air  is  not  absorbed,  and  the  quality  of  the  heat  is  impaired.  An- 
thracite can  be  most  successfully  burnt,  when  blast  is  applied  to  it. 

Fig.  90  exhibits  a  horizontal  section  of  the  furnace.     The  hearth 

Fig.  90. 


Anthracite  double  puddling  furnace,  horizontal  section. 

and  grate  are  seen  from  above.  In  a  double  furnace,  the  grate 
commonly  measures  three  by  five,  and  in  a  single  furnace,  three 
by  four  feet.  The  width  of  the  furnace  externally  is  from  five  and 
a  half  to  six  feet.  Some  furnaces  measure  even  seven  feet ;  but 
this  is  rare.  The  hearth  is  generally  six  feet  in  length,  and  its 
width  accords  with  that  of  the  furnace.  The  flue  ought  to  mea- 
sure at  least  150  square  inches  ;  and  more  than  that,  if  the  chim- 
ney is  narrow.  However,  a  flue  twenty-four  inches  in  width,  and 
seven  inches  in  height,  may  be  considered  of  good  size.  The  chim- 
ney is  sometimes  of  larger  dimensions  than  necessary.  A  lining 
sixteen  inches  square  is  sufficiently  wide  for  a  double  or  single 
furnace.  A  chimney  high  enough  to  carry  the  hot  gases  out  of 
the  furnace  is,  under  all  circumstances,  sufficient.  The  draught, 
and  consequently  the  heat,  depend  upon  the  blast,  for  which  reason 
it  matters  very  little  what  kind  of  chimney  is  employed. 

The  main  difference  between  this  and  the  single  furnace  is,  that 
in  the  former  there  are  two  work  doors,  one  directly  opposite  the 


MANUFACTURE  OF  WROUGHT  IRON.  273 

other.  Therefore,  two  sets  of  workmen  are  required  at  the  same 
time.  In  this  furnace,  double  the  quantity  of  metal  is  charged, 
and  of  course  the  yield  is  twice  that  of  a  single' apparatus.  The 
advantages  of  this  arrangement  are  obvious.  Rooms,  building  ex- 
penses, and  fuel  are  economized,  and  much  of  the  labor  of  the 
workmen  saved.  Besides,  but  one  good  puddler  is  required  for 
managing  the  operation  ;  while  at  a  single  furnace  two  are  needed. 
Of  course,  no  more  repairs  are  required  for  one  furnace  than  for 
the  other. 

The  arrangement  of  the  hearth  in  a  double  furnace  varies  con- 
siderably. In  Pennsylvania  and  the  anthracite  region,  the  boshes 
are  made  of  soapstone,  a  refractory  material  found  in  eastern  Penn- 
sylvania and  New  Jersey.  In  some  places,  they  are  made  of  a 
refractory  ore,  magnetic  oxide,  mixed  with  soapstone.  In  the 
State  of  New  York,  and  the  New  England  States,  the  furnaces 
are  provided  with  hollow  iron  boshes  ;  and  where  anthracite  is  em- 
ployed, the  blast  is  led  through  these  boshes,  and  the  air,  thus 
heated,  applied  to  the  coal.  In  many  cases,  where  the  boshes  are 
of  iron,  iron  ore  is  used,  partly  to  protect  the  boshes,  and  partly  to 
flux  the  iron.  On  the  Hudson  River,  the  crystalized  magnetic  ore 
from  Lake  Champlain,  an  excellent  article,  is  employed  for  this 
purpose.  The  following  illustration  (Fig.  91)  of  the  cast  iron  Iioi- 

Fig.  91. 


Double  furnace  with  air  boshes  and  heating  stove. 

low  boshes  will  be  understood  without  any  description.  Their 
height  is  usually  from  twelve  to  fifteen  inches  ;  their  width  at  the 
bottom  six,  and  at  the  top  from  three  to  four  inches ;  the  inside 
slopes  toward  the  centre.  These  plates  are  generally  so  arranged 
18 


274  MANUFACTURE   OF  IRON. 

that  the  whole  is  cast  in  two  parts,  and  divided  at  the  doors.  Each 
part  forms  a  bridge,  and  its  two  wings  serve  to  form  the  sides. 

There  is  no  difference  between  the  manipulations  at  this,  and 
those  at  the  single  furnace.  It  can  be  used  either  for  puddling  or 
for  boiling  ;  or,  at  least,  a  process  analogous  to  boiling.  That  is  to 
say,  the  fermentation  is  carried  to  half  the  extent  of  that  usual  in 
regular  boiling.  At  one  time,  this  furnace  labored  under  a  serious 
disadvantage.  The  quantity  of  iron  it  contained  at  once,  sometimes 
amounted  to  900  pounds.  Therefore,  the  time  necessary  for  shin- 
gling at  the  hammer,  or  the  old-fashioned  squeezer,  was  not  only 
injurious  to  the  iron,  but  occasioned  a  loss  of  time  to  the  workmen. 
This  difficulty  is  at  present  effectually  removed  by  Burden's  rotary 
squeezer. 

I.  At  the  Eastern  establishments,  the  heating  stove  is  commonly 
applied  to  the  puddling  furnace.  It  forms  an  appendage  or  pro- 
longation of  the  hearth.  Its  location  is  generally  between  the  pil- 
lars of  the  stack.  It  is  charged  from  behind,  and  on  this  account 
is  very  convenient.  Fig.  91  shows  the  arrangement  of  this  stove. 
With  experienced  workmen,  it  affords  facilities  for  economizing 
fuel  and  time ;  but  with  awkward  workmen,  it  is  of  doubtful  utility. 

Before  we  give  the  general  practical  rules  which  should  guide  us 
in  our  manipulations,  we  shall  present  two  very  interesting  illus- 
trations of  puddling. 

m.  Fig.  92  represents  a  section  of  a  single  furnace  in  operation 

Fig.  92. 


Single  puddling  furnace  at  Hyanges. 

at  Hyanges,  France.  The  general  appearance  of  this  resembles 
that  of  any  other  puddling  furnace,  with  the  exception  of  the  manner 
in  which  the  heating  stove  is  applied.  In  this  instance,  it  forms  a 
prolongation  of  the  hearth,  while  the  flue  is  behind  it,  leading  to  the 
stack.  Bituminous  coal  is  used,  and  the  grate  is  constructed  in 


MANUFACTURE   OF   WROUGHT  IRON.  275 

accordance  with  this  circumstance.  Thus  far  there  is  nothing  un- 
usual in  this  furnace.  Its  characteristic  feature  is,  that  its  bottom 
is  of  cast  iron,  which  is  from  four  to  five  inches  thick.  The  fire 
bridge  is  about  six  inches  high ;  the  flue  bridge,  formed  by  the  stove, 
is  of  the  same  height.  At  the  centre,  the  bottom  is  four  inches 
deeper  than  at  the  sides,  and  is  about  four  and  a  half  feet  in  width 
by  five  feet  in  length.  It  is  secured  from  below  by  iron  props,  and 
therefore,  when  burnt  or  cracked,  may  be  replaced  by  a  new  one. 

In  this  furnace,  the  worst  kind  of  coke  iron  is  converted  into 
fibrous  bar  iron  of  very  fine  appearance ;  but  for  the  blacksmith's 
use,  this  article  is  of  poor  quality.  To  those  manufacturers  who 
desire  to  produce  cheap  iron,  with  no  special  regard  to  quality,  this 
furnace  is  worthy  of  imitation.  The  pig  iron  of  Hyanges  is  smelt- 
ed from  a  brown,  fossiliferous  ore  resembling  the  fossiliferous  ore 
of  Eastern  Pennsylvania.  It  is  run  into  large  chills,  directly  from 
the  blast  furnace,  and  cooled  off  as  at  a  running-out  fire. 

After  being  properly  heated,  the  furnace  is  charged  with  a  small 
wheelbarrowful  of  hammer  cinder,  mixed  with  pounded  feldspar. 
The  metal  in  the  stove,  previously  charged  and  red  hot,  is  drawn 
by  the  puddler  upon  the  cinder.  The  furnace  is  then  closed,  and  a 
good  fire  prepared.  Within  a  quarter  of  an  hour,  the  metal  will  be 
sufficiently  heated  for  working ;  that  is,  it  will  be  red  hot,  though  not 
melted.  The  puddler  commences  to  break  up  the  iron,  and  mix  it 
with  the  cinder ;  the  mass  is  gradually  fused,  and  the  cinder  and 
iron  exhibit  a  tendency  to  rise.  At  this  stage  of  the  process,  the  tap 
hole  is  opened,  and  the  main  body  of  cinder  let  out.  Only  a  suffi- 
cient amount  is  retained  to  work  the  iron.  In  the  mean  time,  a  good 
fire  is  prepared  ;  and  the  puddler  draws  the  damper  as  soon  as  the 
cinder  has  flowed  out.  The  refuse  cinder  is  then  covered  with 
ashes,  and  the  operations  vigorously  prosecuted.  If  well  conducted 
— and  this  consists  only  in  quick  work,  for  the  iron  comes  to  nature 
when  the  surplus  cinder  is  gone — the  whole  process  will  be  com- 
pleted in  an  hour.  When  the  balls  are  finished,  and  the  door  closed 
up  for  a  final  heat,  the  metal  is  charged  into  the  stove,  after  which 
it  is  drawn  and  shingled.  The  process  is  then  again  commenced, 
and  continued  as  before. 

At  this  furnace,  but  one  workman  is  required  at  a  time.  A  heat 
is  commenced  and  finished  by  one  man,  without  any  help;  the 
next  heat  is  worked  by  another  puddler.  Some  workmen  employ 
a  boy  for  stirring  the  fire ;  but  this  is  not  always  the  case,  for  the 
boy  must  be  paid  from  their  own  earnings.  At  the  time  we 


276  MANUFACTURE   OF  IRON. 

visited  the  works  at  Hyanges  (1837),  250  kilogrammes  (equal  to 
550  pounds)  formed  a  charge ;  and  nine  or  ten  heats  were  made 
in  twelve  hours,  the  workmen  changing,  however,  at  every  six 
heats.  With  four  workmen,  a  single  furnace  furnished  from  twenty 
to  twenty-five  tons  of  iron  per  week ;  a  great  deal  of  which  time 
was  consumed  in  shingling  the  balls.  By  the  use  of  Burden's 
squeezer,  thirty  tons  per  week  could  be  produced.  The  manipula- 
tion at  the  Hyanges  furnace  differs  from  that  at  common  furnaces 
in  the  fact  that  the  puddling  is  done  on  a  red  hot  iron  bottom,  as 
well  as  in  the  fact  that  a  feldspar  flux  is  added  to  the  cinder.  In 
another  place,  we  shall  investigate  the  reasons  why  this  process 
differs  so  materially  from  the  common  puddling  operations. 

n.  During  a  period  of  three  or  four  years  (from  1834  to  1838), 
we  were  placed  in  a  position  which  required  the  highest  degree  of 
perseverance.  We  engaged  in  the  most  difficult  enterprises,  with 
the  object  of  improving  the  puddling  operations  ;  sometimes  with 
success,  and  at  other  times  failing  to  accomplish  what  we  had  pro- 
posed to  ourselves  as  the  result  of  our  labors.  The  results  of  the 
experience  thus  acquired,  it  is  our  purpose  to  relate,  with  the  hope 
that  they  may  prove  useful  to  those  engaged  in  this  difficult  depart- 
ment of  labor. 

In  the  years  intervening  between  1832  and  1836,  great  exertions 
were  made  by  iron  manufacturers  to  improve  the  quality,  and  to 
increase  the  quantity,  of  iron,  by  means  of  artificial  fluxes.  It  was 
already  a  matter  of  conviction  amongst  educated  metallurgists,  that 
the  quality  of  the  metal  in  the  furnace  depended  upon  the  accom- 
panying cinder.  The  conclusion  very  naturally  followed,  that,  if 
we  could  prepare  a  cinder  of  given  quality,  the  desired  metal 
might  be  obtained  with  comparative  ease.  However  true  the  funda- 
mental premise  may  be,  the  sequel  proved  either  that  the  conclusion 
was  only  measurably  true,  or  that  a  cinder  answering,  in  every 
respect,  our  wishes,  remained  yet  a  desideratum.  In  the  investiga- 
tion of  this  subject,  numerous  experiments  were  made,  in  which  we 
participated.  In  applying  the  artificial  composition  of  cinder  to  the 
puddling  furnace,  subsilicates  of  such  remarkable  fusibility  resulted, 
that  the  best  fire  brick  was,  after  a  few  heats,  entirely  destroyed. 
But  a  settled  conviction  was  arrived  at,  that  the  injurious  admixtures 
of  a  metal  no  longer  formed  an  obstacle  in  furnace  operations ;  for 
phosphorus,  sulphur,  and  silex  were  so  completely  removed  from 
the  iron,  that  no  difference  appeared  to  exist  between  the  best  and 
the  worst  metal.  On  the  contrary,  there  was  reason  to  believe  that 


MANUFACTURE    OF  WROUGHT   IRON. 


277 


the  advantage  was  on  the  side  of  the  inferior  metals.  How  far  the 
latter  conclusion  is  true,  we  shall  hereafter  see.  In  consequence  of 
the  destruction  of  the  hearth,  we  lined  the  furnaces  with  cast  iron, 
wrought  iron,  and  other  refractory  materials  ;  but  all  to  no  purpose. 
The  uniform  result  was,  that  the  cinder  was  either  too  fusible,  or 
that  the  iron  manufactured  was  so  hard  and  tough  as  to  require  a 
heat  which  no  lining  could  withstand.  After  innumerable  experi- 
ments, we  succeeded  in  constructing  a  double  furnace  with  water 
boshes.  At  first,  this  answered  every  purpose ;  but  how  it  suc- 
ceeded where  we  had  to  deal  with  different  metals,  we  shall  relate 
in  another  place.  Nevertheless,  from  the  construction  of  that  fur- 
nace, the  principle  was  established  which,  with  proper  modifica- 
tions, is  applicable  in  all  cases.  As  this  principle  was  the  basis 
of  all  subsequent  modifications,  and  as  it  was  extensively  adopted 
throughout  the  Continent  of  Europe,  we  shall  present  an  engraving 
of  the  furnace,  and  notice  in  another  place  the  alterations  which 
it  has  since  received. 

Fig.  93  represents  a  vertical  section  of  the  double  furnace.  The 
boshes  are  heavy  cast  iron  plates,  ten  inches  high,  five  inches  thick,, 
and  with  a  small  passage  of  about  an  inch  or  an  inch  and  a  half 

Fig.  93. 


Double  furnace  with  water  boshes. 
Fig.  94. 


Ground-plan  of  a  puddling  furnace  with  water  boshes. 


278  MANUFACTURE   OF   IRON. 

bore.  They  extend  all  around  the  hearth  ;  being  coupled  at  one 
door.  At  the  other,  the  water  has  entrance  and  exit.  But  very 
little  water  is  required  to  keep  these  boshes  cool.  The  bottom  of 
the  furnace  is  formed  of  small  cast  iron  plates,  about  twelve  inches 
in  width ;  their  length  corresponding  with  the  width  of  the  furnace. 
The  grate  measures  three  feet  in  width  by  two  feet  in  length ; 
length  of  hearth  six  feet,  and  width  between  the  doors  five  feet. 
Stack  forty  feet  in  height,  and  diameter  of  lining  eighteen  inches. 
"Width  of  flue  twenty-four  inches ;  height  six.  Distance  between 
the  iron  bottom  of  the  furnace  and  the  brick  roof  twenty-eight 
inches.  The  lower  parts  of  the  furnace  are  open,  so  as  to  permit 
a  free  circulation  of  air  to  cool  the  bottom. 

This  furnace  works  exceedingly  well  in  all  cases  in  which  infe- 
rior cold  or  hot-short  iron,  smelted  by  heavy  burden,  is  puddled. 
From  any  fusible  metal,  that  is,  from  any  metal  smelted  by  heavy 
burden,  or  by  low  temperature,  very  superior  iron  may  be  puddled 
by  the  application  of  artificial  fluxes.  Iron  equal  to  the  best  char- 
coal iron  may  be  manufactured  from  cold-short,  or  from  any  very 
fusible  metal.  But  for  gray  metal  of  small  burden,  particularly 
for  all  coke,  stone  coal,  or  hot  blast  iron,  these  furnaces  are  of 
questionable  utility.  Eor  white  metal  they  are  perfectly  useless. 
We  failed  invariably  in  our  attempts  to  work  white  metal  of  small 
burden,  whether  it  belonged  to  the  best  quality,  or  whether  it  was 
smelted  by  coke  or  anthracite,  or  hot  blast. 

o.  The  manipulation  in  this  furnace  does  not  differ  from  that  pre- 
viously described ;  but,  as  the  application  of  artificial  fluxes  is  not 
practically  so  well  understood,  we  shall  briefly  describe  it.  This 
furnace  is  not  adapted  for  puddling,  or  for  the  working  of  white 
metal,  but  for  boiling  alone.  It  is  heated  in  the  same  manner  as 
any  other  furnace.  Cinder  is  filled  and  melted  as  described  when 
speaking  of  the  Pittsburgh  furnace.  At  the  close  of  every  heat,  a 
portion  of  cinder  is  let  off,  in  case  too  much  exists  at  the  bottom. 
But  this  is  not  likely  to  be  the  case,  if  due  care  is  observed.  When 
the  cinder  at  the  bottom  is  cooled  off,  the  metal  is  charged  in  the 
middle  of  the  furnace.  This  may  be  taken  from  the  heating  stove, 
in  case  one  is  connected  with  the  furnace.  Should  there  be  a  good 
fire,  it  will  be  ready  for  work  in  half  an  hour,  when  it  may  be  broken 
up,  and  mixed  with  the  cinder.  When  the  pig  iron  is  bad,  that  is, 
cold-short  or  hot-short ;  or  where  it  contains  sulphur,  phosphorus, 
and  silex,  besides  carbon,  the  fire  should  be  well  stirred,  without 
charging  fresh  coal,  and  the  temperature  raised  sufficiently  high  to 


MANUFACTURE   OF  WROUGHT  IRON.  279 

rnelt  the  iron  perfectly;  otherwise  we  cannot  produce  a  good  article. 
Whether  the  iron  is  melted,  and  not  merely  mixed  with  the  cinder, 
may  be  known  by  the  formation  of  bright  streaks  in  it.  When  the 
mass  is  thoroughly  liquid,  the  damper  may  be  almost  completely 
shut ;  still,  the  interior  of  the  furnace  should  be  bright,  though  the 
flame  is  not  visible.  The  artificial  flux  is  now  thrown  into  the  fur- 
nace, at  intervals  of  one  minute.  Assuming  this  flux  to  be  divided 
into  ten  or  twelve  portions,  all  of  it  may  be  applied  in  fifteen 
minutes.  During  this  application,  iron  of  good  quality  rises ;  but 
that  which  is  bad,  or  very  liquid,  rises  only  by  means  of  hammer- 
slag  or  water.  Before  the  cinder  rises,  blue  flames,  in  many  cases, 
literally  cover  the  surface ;  but  cease  when  the  iron  comes  to 
nature,  that  is,  shows  itself  at  the  surface  in  little  specks.  One 
hour  is  sufficient  for  this  part  of  the  process,  that  is,  from  the 
charging  till  the  appearance  of  the  refined  iron.  Some  metals  work 
slowly ;  but  this  difficulty  may  be  remedied  by  the  construction  of 
the  furnace.  When  the  iron  is  refined,  that  is,  when  it  boils 
strongly,  and  begins  to  rise,  the  damper  may  be  raised,  and  fresh 
coal  applied.  The  boiling  will  thus  be  brought  to  a  stop.  By 
gradually  increasing  the  heat,  working  fast,  and  turning  the  finished 
iron,  which  is  now  in  spongy,  open  lumps,  the  cinder  rapidly  sinks, 
and  the  iron  is  left  bare,  ready  for  balling.  If  the  depth  of  the 
boiling  cinder,  at  its  highest  point,  is  five  or  six  inches,  one  turn- 
ing will  be  sufficient;  but  if  ten  or  twelve  inches,  the  iron  gene- 
rally becomes  so  cold  in  the  bottom,  that  a  turning  back  and  for- 
ward several  times  is  required.  If  this  kind  of  boiled  iron  is  balled 
up  cold,  it  will  break  under  the  hammer  or  squeezer,  of  whatever 
quality  it  may  be.  The  responsibility  of  .this  department  rests  upon 
the  puddler.  This  process  differs  from  other  processes  principally 
in  the  melting-in  of  the  metal.  The  more  inferior  the  metal,  the 
more  carefully  should  this  be  performed. 

If  the  metal  is  of  poor  quality,  a  charge  should  never  exceed  700 
pounds;  but  if  otherwise,  it  may  be  increased  to  800,  and  even 
900  pounds.  Bad  pig  iron,  though  inclined  to  work  slowly,  may 
be  worked  quite  as  fast  as  that  which  is  good,  if  the  charges  are 
small.  The  quality  of  puddled  iron  may  be  made  equally  good 
under  all  circumstances.  Pig  iron  may  contain  phosphorus,  sul- 
phur, or  any  injurious  admixture  except  copper.  Puddled  iron 
may  be  completely  freed  of  them.  Bar  iron  manufactured  from 
the  most  cold-short  gray  pig  iron  which  contains  phosphorus,  may 


280  MANUFACTURE    OF  IRON. 

be  made  superior,  in  every  respect,  to  that  manufactured  from  the 
best  metal. 

VI.   G-eneral  Remarks  on  Charcoal  Forges. 

It  is  undeniable  that  charcoal  forge  iron  is,  in  many  respects, 
superior  to  puddled  iron.  For  all  the  purposes  for  which  wrought 
iron  is  applied,  it  is  more  malleable,  compact,  and  durable.  The 
puddling  process  is  conducted  on  more  philosophical  principles  than 
the  charcoal  forge,  and  in  the  course  of  time  may  be  brought  to 
such  a  state  of  perfection  as  to  supersede  the  latter  altogether.  But 
this  is  not  the  case  at  present;  and  the  charcoal  forge  will  be  needed 
so  long  as  the  puddling  process  does  not  furnish  a  quality  of  iron 
equal  to  it.  Another  reason  why  the  former  will  command  prece- 
dence for  some  time  to  come,  is  that  it  is  less  expensive  than  the 
more  complicated  puddling  establishments,  and  permits  the  manu- 
facture of  iron  on  a  small  scale  without  serious  disadvantages.  Iron 
works,  situated^  at  remote  places  in  the  country,  frequently  find  a 
favorable  market  for  a  limited  quantity  of  iron ;  while  an  increase 
of  that  quantity  would  not  prove  profitable.  Such  cases  are  very 
common  in  the  farming  districts  of  the  interior  of  the  country  which 
are  not  easily  accessible,  as  well  as  in  the  growing  Western  States. 
The  same  remark  is  applicable  to  the  new  States  and  territories. 
It  is  questionable  whether  the  charcoal  forges  of  the  West,  and 
even  in  the  heart  of  the  anthracite  and  bituminous  basin,  do  not 
yield  larger  profits  than  the  puddling  forges  and  rolling  mills  ;  at 
least,  an  investment  in  charcoal  establishments  may  be  considered 
quite  as  safe  as  in  those  of  stone  coal,  at  the  present  time. 

a.  The  location  of  charcoal  forges  should  depend  upon  the  sup- 
ply of  ore  and  wood.  Inferior  ore,  and  the  metal  smelted  from  it, 
are  less  useful  to  the  charcoal  fire  than  to  the  puddling  furnace. 
The  success  of  the  former  depends  upon  the  quality  of  the  metal  with 
which  it  is  supplied.  It  is  thus  evident  that  the  best  is  always  the 
cheapest  metal.  This  rule  is  not  applicable  to  puddling  establish- 
ments. In  addition  to  this,  the  charcoal  forge  requires  good  coal. 
But  rich  ore  or  excellent  metal  may  counterbalance  expensive  coal ; 
while  poor  metal  and  expensive  coal  will  yield  only  unprofitable 
results.  Where  the  metal  is  good,  a  ton  of  iron  requires  only  150, 
and  sometimes  only  120  bushels  of  charcoal ;  and  seven  tons  can 
be  produced  in  a  week,  with  but  one  fire.  But  where  it  is  poor,  a 
ton  will  require  from  200  to  300  bushels ;  while  only  two  or  three 
tons  of  iron  per  week  will  be  produced.  We  refer  to  blooms,  not 


MANUFACTURE  OF  WROUGHT  IRON.  281 

to  drawn  iron.  Consequently,  should  the  iron  resulting  from  the 
smelting  of  good  or  bad  metal  be  equally  valuable,  which  is  not  a 
fact,  the  expenses  of  manipulation  are  so  decidedly  in  favor  of  the 
former,  that  the  question  which  to  choose  will  never  arise. 

b.  The  magnetic  ores  of  the  States  of  New  York,  Vermont,  New 
Jersey,  Missouri,  afford  an  excellent  article  for  the  charcoal  forge. 
These  ores  exist  in  such  immense  quantity,  and  in  the  north-west 
part  of  New  York  are  of  such  superior  quality,  that  the  little  inte- 
rest they  excite  in  the  public  mind  is  to  us  a  matter  of  extreme 
astonishment.     In  the  magnificent  region  just  mentioned,  metal 
might  be  made  at  the  ore  banks,  and  sent  to  the  Hudson  or  the 
Delaware  River  to  be  puddled.     The  spathic  carbonate,  the  specu- 
lar ore,  and  the  red  clay  ores  of  the  transition  series,  also  consti- 
tute an  excellent  article  for  the  charcoal  forge;  but  these  are  not 
so  generally  distributed  as  the  magnetic  ore  ;  at  least,  they  are  not 
concentrated  in  such  large  masses  at  any  given  place.     The  rich 
hydrates  of  Tennessee  and  Alabama  are  adapted  for  the  Catalan 
forge.      The  same   reasons  which  may  be    assigned  against  the 
working  of  poor  ores  in  this  forge,  apply  against  their  use  in  the 
charcoal  blast  furnace.     Inferior  metal  is,  at  present,  employed  in 
the  coal  regions  for  the  manufacture  of  charcoal  blooms  ;  but  we 
predict  that  these  efforts  will,  in  a  short  time,  be  abandoned,  be- 
cause poor  charcoal  iron  cannot  successfully  compete  against  pud- 
dled iron.     Metals  which  contain  phosphorus  or  sulphur  are  not 
adapted  for  the  charcoal  forge,  because  of  the  inferior  iron  they 
produce,  and  because  of  the  amount  of  time  consumed  in  convert- 
ing them  into  bar  iron.     Gray  metal  from  rich  ores,  and  mottled 
or  white  metal  of  pure  origin,  form  medium  qualities.     All  metals 
derived  from  impure  bog  ores,  sulphurets,  silicious  ore,  and  ores 
containing  phosphorus ;    all  the  gray  metals  smelted  from  poor 
ores,  particularly  those  of  silicious  origin  ;  and  all  white  metal 
resulting  from  small  burden,  inferior  ore,  and  bad  management  in 
the  blast  furnace,  are  improper  for  the  charcoal  forge. 

c.  The  necessity  of  good  metal  in  the  forge  is  illustrated  by  the 
following  fact:  An  instance  is  recorded  in  which  a  ton  of  blooms, 
from  white  metal  of  excellent  quality,  was  produced,  with  the  con- 
sumption of  only  ninety  bushels  of  coal ;  while,  on  the  other  hand, 
when  gray  pig  iron  was  used,  400  bushels  of  coal  were  consumed 
in  producing  the  same  amount. 

d.  The  site  of  a  forge  is  generally  selected  in  relation  to  facili- 
ties for  obtaining  water  power ;  but  it  is  probable  that  steam  may 


282  MANUFACTURE    OF   IRON. 

prove  to  be  the  preferable  power,  because  the  waste  heat  of  the 
forge  fire  is  sufficient  to  generate  it.  It  is  also  probable  that  the 
first  outlay  in  erecting  the  works  is,  at  least  in  a  majority  of  in- 
stances, in  favor  of  the  steam-engine. 

e.  The  application  of  hot  blast  to  the  charcoal  forge  is  of  ques- 
tionable advantage.  It  will  save  fifteen  or  twenty  per  cent,  of 
coal ;  but  labor  is  increased,  and  the  iron  depreciated.  We  shall 
elsewhere  make  some  additional  remarks  on  this  subject. 

VII.   General  Remarks  on  Puddling. 

This  method  of  converting  cast  iron  into  malleable  iron  is  de- 
signed to  supersede  every  other  method  by  which  that  result  is 
effected.  But,  thus  far,  the  quality  of  puddled  iron  has  been 
such  that  we  have  been  unable  entirely  to  dispense  with  the  char- 
coal forge.  Still,  this  quality  would  be  much  improved  if  better 
metal  was  generally  employed.  The  nature  of  the  puddling  pro- 
cess is  such,  as  we  have  elsewhere  stated,  that  we  are  enabled  by 
it  to  employ  inferior  metals  to  a  great  degree.  Thus,  blast  furnaces 
have  been  erected  at  places  where  charcoal  forges  would  not  have 
flourished.  Inferior  pig  iron  answers  tolerably  well  for  the  pud- 
dling furnace.  Metal  perfectly  useless  in  the  charcoal  fire  will, 
in  this  furnace,  produce  a  very  good  article.  In  fact,  every  kind 
of  pig  iron,  however  bad  in  quality,  may,  by  the  puddling  process, 
be  advantageously  worked. 

a.  In  the  Western  States,  where  charcoal  pig  alone  is  puddled 
and  boiled  in  single  furnaces,  iron  of  very  good  quality  is  made. 
A  great  deal  of  inferior  iron  is  also  produced,  which,  according  to 
the  metal  used,  should  be  of  better  quality.  The  puddling  fur- 
naces of  the  West  work  well ;  but  it  is  doubtful  whether  a  due 
amount  of  labor  is  spent  in  working  the  iron.  The  puddlers  gene- 
rally finish  a  heat  in  less  than  an  hour  and  a  half,  including  shin- 
gling; and  the  boilers  in  less  than  two  hours.  At  other  places,  this 
is  considered  an  insufficient  time  to  do  full  justice  to  the  work.  At 
well-regulated  Eastern  establishments,  twelve  hours  are  consumed 
for  five  boiling  heats,  and  the  same  time  for  six  puddling  heats. 
This  may  be  considered  fair  time  for  industrious  and  judicious 
manipulation.  Where  the  metal  is  of  superior  quality,  less  atten- 
tion is  required.  But  throughout  the  United  States  the  tendency 
of  most  blast  furnaces  is  to  produce  gray  metal ;  consequently,  the 
manufacture  of  good  bar  iron  requires  great  industry,  however 
good  may  be  the  ore  from  which  it  is  smelted. 


MANUFACTURE  OF  WROUGHT  IRON.  283 

5.  As  previously  remarked,  at  Pittsburgh  and  the  Western  Works, 
boiling  is  carried  on  in  about  one-half  of  the  puddling  furnaces. 
Those  used  exclusively  for  puddling  are  regarded  as  necessary  evils, 
and  are  employed  merely  to  make  cinder  for  the  boiling  furnaces. 
Excellent  cinder  is  produced  from  metal  of  good  quality,  carefully 
puddled  ;  but,  on  account  of  the  refining  of  the  crude  iron  before  it 
is  taken  to  the  furnace,  this  operation  is  expensive.  All  the  advan- 
tages which  the  process  includes  are  realized  at  the  Western  estab- 
lishments. But,  unless  other  methods  are  adopted  by  the  Western 
manufacturers  in  working  pig  metal,  competition  will  gradually 
exhaust  all  the  profits  of  this  business.  This,  let  us  observe,  is  a 
more  important  matter  than  it  seems  to  be,  for,  if  puddling  is  re- 
placed altogether  by  boiling,  the  question  meets  us,  whence  is  the 
necessary  supply  of  cinder  to  be  obtained  ?  Charcoal  forge  cinder, 
at  present  frequently  applied,  cannot  be  obtained  in  sufficient  quan- 
tity. Artificial  fluxes,  then,  are  the  only  resource  of  the  Western 
manufacturers.  Good  iron  ore  will  serve  as  an  excellent  flux ;  but 
this  cannot  be  found  either  in  the  Western  or  in  the  Eastern  coal 
regions.  In  the  State  of  New  York,  the  magnetic  ore  from  Lake 
Champlain  is  employed ;  and  the  furnaces  of  this  State  not  only 
produce  excellent  iron,  but  furnish  a  more  abundant  yield  than 
any  we  have  ever  seen.  At  Saugarties,  on  the  Hudson  River, 
2000  pounds  of  rough  bars  have  been  made  from  an  amount  of  pig 
iron  varying  from  2075  to  2100  pounds.  Loss  only  from  three  to 
five  per  cent.  Amount  of  anthracite  coal  consumed  from  1600  to 
1TOO  pounds.  Furnaces  double,  with  iron  air  boshes ;  charge  750 
pounds,  and  five  heats  in  twelve  hours. — The  magnetic  ores  of 
Missouri,  and  the  red  oxides  of  Arkansas  afford  a  good  material  for 
the  Western  mills  ;  but  ores  of  the  coal  formation  are  not  sufficiently 
pure.  The  amount  of  good  ore  required  per  ton  of  inferior  pig  iron 
is  sometimes  from  400  to  500  pounds  ;  but  for  excellent  metal, 
rarely  beyond  200  pounds. 

c.  We  have  stated  that  most  puddling  furnaces  are  provided  with 
iron  boshes.  But  in  those  which  work  anthracite  iron,  soapstone 
is  employed  for  keeping  the  boshes  in  order.  It  is  evident  that,  if 
iron  boshes  were  proved  in  all  cases  to  be  advantageous,  they 
would  be  adopted.  But,  in  the  present  case,  they  are  of  doubtful 
utility,  as  we  shall  explain. 

The  necessity  of  enlarging  the  hearth,  so  that  a  smaller  surface 
of  the  boshes,  in  proportion  to  a  given  amount  of  metal,  would 
become  cool,  originated  the  double  furnace.  It  was  found  that  tho 


284  MANUFACTURE   OF  IRON. 

cooling  influence  of  the  iron  lining,  in  small  or  single  furnaces,  was 
so  great  that  inferior  pig  iron  could  not  receive  that  improvement 
which  otherwise  might  be  effected  with  comparative  ease.  The 
extension  of  the  area  of  the  hearth,  to  a  great  extent,  removed  this 
difficulty.  There  is  no  doubt  that  the  quality  of  iron  might  be 
improved  to  an  inconceivable  degree,  if  a  hearth  could  be  con- 
structed of  materials  adapted  to  resist  the  action  of  strong  alkalies; 
but  the  necessity  of  cooling  the  boshes  is  so  strong  a  counteracting 
element,  that  the  beautiful  theory  of  improving  iron  by  means  of 
artificial  cinder  is  but  of  limited  application.  In  this  respect, 
double  furnaces  present  greater  advantages  than  single  furnaces ; 
and  boshes  cooled  by  air  are  superior  to  those  cooled  by  water. 

In  the  improvement  of  bad  pig  iron,  by  puddling,  our  primary 
object  should  be  to  melt  it  perfectly,  and  then  to  remove  its  impuri- 
ties by  means  of  cinder.  If,  therefore,  a  hearth  is  so  cold  as  to 
prevent  the  melting  of  the  metal,  the  most  essential  condition  of 
improvement  is  not  realized.  If  the  iron  contains  impurities  firmly 
and  intimately  combined — as  that  from  coke,  anthracite,  or  even 
from  charcoal  furnaces,  smelted  with  small  burden — a  perfect  re- 
melting  is  necessary.  Such  iron  requires  a  strong  heat ;  and  this 
heat  cannot  be  produced  in  a  furnace  with  cooled  boshes.  Hence 
the  failure  of  experiments  made  to  improve  such  iron.  Anthracite 
iron  contains  a  large  amount  of  silex,  in  addition  to  carbon ;  and  a 
furnace  with  water  boshes  is  unable  to  produce  a  heat  sufficient  to 
melt  it.  Fibrous  bar  iron  is  preferable,  as  an  article  of  commerce, 
to  that  which  is  cold-short ;  and  to  prevent  it  from  becoming  cold- 
short, the  intimate  connection  between  the  impurities  and  the  iron 
must  be  destroyed.  Therefore,  a  furnace  with  soapstone,  or,  what 
is  still  better,  good  fire  brick,  will  produce  a  better  iron  for  the 
market  than  a  furnace  with  cold  boshes.  A  uniform  temperature 
of  the  lining  and  walls  is  required  to  produce  a  thorough  solution 
of  the  pig  iron.  The  presence  of  silex  in  large  amount,  as  in  a 
lining  of  soapstone  or  fire  brick,  affords,  by  retarding  the  work, 
every  facility  for  producing  this  result.  This  latter  circumstance 
should  be  viewed  rather  as  the  least  of  several  evils  than  as  a  posi- 
tive advantage. 

From  these  considerations,  it  follows  that  pig  iron  from  small  bur- 
den, or  made  by  a  high  temperature  in  the  blast  furnace,  cannot  be 
improved  in  a  furnace  with  water  boshes  ;  and  that  the  application 
of  these  boshes  should  be  limited  to  such  iron  as  will  thoroughly 
melt  at  a  medium  heat.  Consequently,  white  metal  containing  a 


•      MANUFACTURE   OF  WROUGHT  IRON.  285 

large  amount  of  carbon,  anthracite,  coke,  and  charcoal  iron  from 
small  burden  and  hot  blast,  as  well  as  all  refined  metal,  are  ex- 
cluded. Pig  iron  from  heavy  burden,  and  from  ores  containing 
phosphorus ;  gray  charcoal  pig ;  and,  in  fact,  all  metal  which 
readily  melts,  and  keeps  liquid  for  a  considerable  time,  are,  of  all 
others,  the  most  serviceable. 

d.  Our  own  experience,  which  is  somewhat  extensive  in  this 
branch  of  the  business,  proves  that  white  metal  from  the  richest 
ores  is  unfit  to  be  worked  at  all  in  a  furnace  with  a  cooled  hearth ; 
and  produces  far  better  iron  in  brick  linings.  Pig  iron  from  small 
burden  and  coke,  we  never  succeeded  in  improving.  With  white 
iron  from  charcoal  furnaces  and  small  burden  we  were  equally  un- 
successful. The  most  favorable  pig  iron  is  that  which  is  made  by 
a  small  quantity  of  coal  and  by  low  temperature  in  the  blast  fur- 
nace. The  lower  the  temperature,  the  better  the  iron.  Pig  iron 
smelted  from  phosphates,  is  easily  converted  into  the  best  kind  of 
bar  iron,  if  the  temperature  of  the  furnace  has  been  low,  or  the  bur- 
den heavy ;  but  if  smelted  from  the  same  ore,  and  by  a  high  heat, 
whether  charcoal,  anthracite,  or  coke,  it  is  improved  with  difficulty ; 
sometimes  total  failure  results.  The  same  rule  is  applicable  to  pig 
iron  smelted  from  silicious  and  sulphurous  ore.  In  fact,  it  may  be 
laid  down,  as  a  general  rule,  that  the  smaller  the  amount  of  coal 
consumed,  or  the  lower  the  temperature  of  the  hearth  in  the  blast 
furnace,  the  better  will  be  the  quality  of  the  metal ;  that  is,  the 
more  fit  it  will  become  for  improvement  in  the  puddling  furnace. 
We  thus  see  the  advantage  of  heavy  burden  in  the  blast  furnace, 
for  it  not  only  reduces  the  first  cost  of  the  metal,  but  makes  a  far 
superior  article  for  subsequent  operations.  We  may  safely  say, 
that  the  worst  cold-short  or  sulphurous  metal,  smelted  by  a  low 
heat,  is  quite  as  good  as  the  best  metal  from  the  best  ore  smelted 
by  a  high  temperature.  We  will  give  a  practical  illustration. 

About  ten  years  ago  we  were  engaged  in  improving  cold-short 
iron;  that  is,  pig  iron  smelted  from  bog  ore,  which,  before  that  time, 
possessed  no  value  whatever.  Our  manipulations  were  conducted 
in  a  double  furnace,  with  water  boshes.  The  puddling  was  carried 
on  by  means  of  artificial  fluxes.  We  succeeded,  without  difficulty, 
in  producing  a  beautiful  bar  iron,  in  quality  equal  to  the  best  in  the 
market.  With  the  object  of  testing  its  virtues,  a  portion  of  it  was  sent 
to  a  distant  mill,  and  converted  into  wire.  So  successful  was  the 
result,  that  the  puddled  iron  was  preferred  to  the  best  charcoal  iron. 
At  the  wire  mills,  where  an  extensive  business  was  done,  a  large 


286  MANUFACTURE    OF  IRON. 

quantity  of  charcoal  iron  was  needed.     As  this  could  not  be  ob- 
tained in  consequence  of  its  expensiveness,  puddling  works  were 
erected  for  the  purpose  of  furnishing  iron  for  the  inferior  qualities  of 
wire.    At  this  establishment,  steel  metal  of  the  most  superior  kind 
was  wrought,  which  of  course,  puddled  in  single  furnaces,  with 
good  fire  brick  lining,  made  an  excellent  bar  iron.    After  using  the 
iron  of  our  cold-short  metal,  the  owners  of  the  rolling  mill  entered 
into  an  engagement  with  us  by  which  we  bound  ourselves  to  fur- 
nish as  good  an  article  from  their  superior  plate  metal  as  we  had 
made  from  worthless  phosphorous  pig.     A  few  heats  made  in  one 
of  their  own  puddling  furnaces  indicated  that  improvement  was 
possible ;  but,  owing  to  certain  peculiarities  of  the  new  process, 
puddling  could  not  be  performed  in  a  brick  lining.     We  therefore 
concluded  to  erect  a  double  furnace  at  once,  and  apply  iron  boshes. 
Until  that  time,  our  practice  had  been  confined  principally  to  the 
worst  kind  of  pig  iron,  and  accompanied  with  more  or  less  success, 
according  to  the  nature  of  the  metal  with  which  we  had  to  deal. 
We  entered  upon  the  undertaking  with  great  confidence.    The  idea 
of  failure  never  entered  our  mind.  This  confidence  appeared  to  be 
justified  on  account  of  the  insignificance  of  the  improvement  re- 
quired, compared  to  what  we  had  already  arrived  at.     The  metal 
was  the  best  which  the  Continent  of  Europe  afforded  ;  but,  after  all 
our  exertions,  the  ultimate  result  was  a  total  failure.     As  this  is 
one  of  the  most  remarkable  as  well  as  interesting  cases  which  ever 
happened,  we  shall  relate  it  somewhat  in  detail,  and  thus  serve  a 
useful  purpose.     The  metal  used  was  smelted  from  sparry  carbon- 
ates ;  it  was  almost  crude  steel,  that  is,  white  metal  containing  car- 
bon in  large  amount.    Being  thoroughly  acquainted  with  the  most 
important  part  of  the  operation,  we  took  great  care  to  have  a  fur- 
nace of  good  heating  capacity.    The  metal  melted  in  a  short  time, 
and  at  a  low  temperature;  but  the  least  stirring  with  the  tools  made 
it  crystalize,  and  worked  it  into  nature;  and  sufficient  time  was 
not  left  to  enable  us  to  mix  it  properly  with  the  cinder.    The  result 
was  a  dry,  hard  iron  which  broke  under  the  hammer.     No  effort 
was  left  untried  to  overcome  this  apparently  trifling  difficulty;  and 
when  we  at  last  succeeded,  a  very  singular  circumstance  put  a  stop 
to  the  experiments.     The  breaking  of  the  balls  under  the  hammer 
is,  in  all  cases,  the  result  of  too  slow  work.      The  workmen  did 
their  best ;  but  the  iron  worked  too  fast.    This  is  generally  the  case 
with  white  iron  containing  a  great  deal  of  carbon.     The  applica- 
tion of  fluxes  retarded  the  process.    At  last  the  metal  worked  well. 


MANUFACTURE   OF   WROUGHT  IRON.  287 

and  became  soft  and  tenacious  iron.  But,  when  piled  and  re-heated, 
a  number  of  the  bars  broke  in  the  merchant  rollers  ;  and  the  iron, 
commonly  of  a  silvery  white  appearance,  exhibited  in  its  fibres  a 
dark  color.  On  a  second  re-heating,  both  in  a  blacksmith's  fire 
and  the  re-heating  furnace,  it  broke  up  into  small  fragments.  In 
fact,  it  was  iron  no  longer,  but  black  magnetic  oxide.  Rolled  down 
to  half  inch  rods,  it  broke  into  fragments  on  the  first  heat.  Bars 
one  and  two  inches  square  exhibited  on  their  surface  a  high  degree 
of  oxidation,  and  appeared,  internally,  of  a  fibrous,  dull  yellowish 
color.  On  the  application  of  the  slightest  heat,  this  color  changed 
to  black. 

The  above  experiment  is  a  highly  interesting  one.  It  shows 
clearly  the  legitimate  scope  of  improvements,  and  the  direction  in 
which  experiments  should  tend.  The  metal  employed  was,  as  we 
have  stated,  of  the  best  quality.  It  furnished  excellent  steel  with 
the  greatest  facility.  In  the  charcoal  forge,  it  furnished  the  strong- 
est kind  of  bar  iron — consuming  per  ton  of  iron  only  from  110  to 
130  bushels  of  charcoal.  In  the  single  puddling  furnace,  with  brick 
lining,  it  produced  a  firm,  tenacious  iron,  but  of  too  coarse  fibre, 
and  containing  too  much  cinder  for  the  manufacture  of  wire  ;  while, 
in  the  puddling  furnace  with  iron  boshes,  it  did  not  work  at  all, 
and  ultimately  returned  to  its  primitive  condition — that  is,  became 
oxidized  to  ore. 

The  establishment  where  our  first  operations  were  conducted  was 
a  very  inferior  one.  The  metal  used,  whether  in  castings,  charcoal 
forge,  or  puddled  iron,  was  almost  worthless ;  at  least,  it  commanded 
a  very  low  price  in  the  market.  The  pig  iron,  smelted  from  phos- 
phoric ores,  was  cold-short  in  the  highest  degree,  perfectly  useless 
in  the  charcoal  forge,  and  a  poor  article  in  the  common  puddling 
furnace.  Yet  this  worthless  metal  was  converted,  with  the  utmost 
facility,  into  bar  iron  superior  to  any  kind  in  a  market  where  the 
first  quality  of  charcoal  iron  was  alone  saleable.  The  amount  of 
charcoal  consumed  in  the  blast  furnace  was  only  from  80  to  100 
bushels,  notwithstanding  the  ore  yielded  but  twenty  per  cent. ; 
while  from  180  to  200  bushels  were  required  in  producing  a  ton  of 
the  steel  metal  on  which  we  experimented. 

The  experiments  we  have  described  are  extreme  cases  ;  but  they 
exhibit  clearly  the  method  by  which  we  can  arrive  at  the  most 
favorable  results.  We  always  failed  when  we  attempted  to  improve 
white  iron  from  an  overheated  blast  furnace,  even  though  the  ore 
and  coal  were  of  the  best  kind.  We  failed  with  the  best  white 


288  MANUFACTURE   OF   IRON. 

metal  of  the  Continent  of  Europe;  with  the  steel  metal  of  Siegen  and 
Styria ;  with  white  Scotch  pig ;  with  the  white  coke  iron  of  the 
fossiliferous  ore. of  France:  and  with  the  coke  iron  of  the  Mount 
Savage  Iron  Works,  Maryland.  But  we  always  succeeded  in  im- 
proving both  the  quality  and  yield  of  pig  iron  from  a  tolerably  well- 
conducted  blast  furnace  operation. 

e.  Experience  thus  shows  what  is  required  both  for  the  charcoal 
forge  and  the  puddling  furnace.  We  will  recapitulate  the  con- 
clusions arrived  at.  Gray  pig  iron  of  a  fusible  nature  is  ill  adapt- 
ed for  the  former ;  but  is  the  best  of  all  kinds  for  the  latter. 
White  metal  containing  carbon  in  small  quantity,  or  smelted  by 
heavy  burden,  is  good  in  either  case ;  but  white  metal  from  poor 
ores  and  light  burden  is,  in  all  cases,  inapplicable.  White  metal 
from  rich  ore  and  light  burden  is  superior  to  all  in  the  charcoal 
forge,  but  in  the  boiling  furnace  it  is  almost  useless.  We  may 
hence  conclude  that  cold  iron  boshes  are  of  great  advantage  where 
pig  iron  from  a  well-regulated  blast  furnace  operation  is  wrought; 
but  that,  where  white  pig  iron  from  small  burden  and  a  high  tem- 
perature— as  in  coke  and  anthracite  furnaces,  in  which  an  excess 
of  limestone  is  used — is  to  be  converted  into  bar  iron,  they  are  dis- 
advantageous. In  the  latter  case,  a  fire  brick  or  soapstone  lining 
is  preferable. 

/.  Thus  far  we  have  considered  simply  the  best  means  of  making 
wrought  iron.  But  if  we  wish  to  produce  wrought  iron  for  specific 
purposes,  it  is  not  a  matter  of  indifference  what  kind  of  apparatus 
we  employ.  Merchant  iron  should  be  malleable,  fibrous,  and  of 
good  welding  properties.  This,  as  well  as  very  cohesive  wire  iron, 
is  manufactured  in  great  perfection  in  the  charcoal  forge,  and  in  the 
double  puddling  furnace  with  iron  boshes.  But  railroad  iron  should 
not  be  made  in  either  of  these  furnaces.  Easily  welded  iron  is 
made  by  allowing  a  small  portion  of  carbon  to  remain  in  the  metal, 
and  by  expelling,  as  far  as  possible,  all  foreign  matter  from  it. 
But  this,  by  destroying  the  fibre,  will  make  iron  of  large  dimensions 
cold-short.  By  re-heating  and  rolling  small  rods,  the  carbon  will 
evaporate.  If,  therefore,  we  want  fibrous  railroad  or  any  heavy  bar 
iron,  we  must  employ  a  metal  free  from  carbon,  iron  from  which  the 
carbon  is  easily  expelled,  as  that  from  the  run-out  fires.  This  is 
to  be  puddled  in  a  very  warm  furnace.  A  cooled  puddling  hearth 
produces  a  good  welding  iron  ;  but  the  long  exposure  of  large  piles 
of  this  iron — such  as  are  necessary  for  railroad,  heavy  bar  iron,  and 
boiler  plate— to  a  welding  heat,  occasions  great  waste.  In  all  such 


MANUFACTURE  OF  WROUGHT  IRON.  289 

cases,  a  brick  lining  is  preferable  to  cold  boshes.  Wire  iron  should 
be  of  the  best  quality  ;  but  the  puddling  process  by  which  it  is  pro- 
duced would  be  inapplicable  for  railroad  iron,  for  the  latter  would 
thus  become  cold-short.  Iron  designed  for  small  rods,  hoops,  gas 
pipes,  and  wire,  ought  to  exhibit  a  crystaline  fracture,  a  steel-like 
grain,  which  is  produced  by  carbon.  But  of  all  other  foreign  mat- 
ter it  should  be  free.  Silex  and  phosphorus  will  not  evaporate, 
like  carbon,  on  repeated  exposure  to  heat ;  and  iron  which  contains 
either  in  a  non-vitrified  state,  will  be  cold-short  under  all  circum- 
stances, and  will  be  useless  for  wire,  or  for  any  purpose  for  which 
strength  is  required. 

Wire  iron,  or  merchant  iron,  should  be  manufactured  from  gray 
pig,  which,  unless  improved  by  artificial  cinder,  must  be  of  the  best 
quality.  By  boiling  with  artificial  cinder,  any  kind  of  gray  pig 
may  be  converted  into  good  iron  in  the  puddling  furnace  with  iron 
boshes.  In  a  cooled  hearth,  all  foreign  admixtures  can  be  expelled 
from  the  metal,  and  yet  enough  carbon  retained  to  preserve  its 
welding  properties.  This  advantage  is  accompanied  with  a  disad- 
vantage ;  for  the  carbon,  as  we  have  before  stated,  makes  the  iron, 
when  in  large  masses,  cold-short,  and  occasions  waste  in  the  re- 
heating furnace.  Piles  of  700  or  800  pounds  in  weight,  exposed  to 
a  strong  heat  in  the  re-heating  furnace,  will  melt  at  the  surface, 
without  becoming,  in  the  interior,  sufficiently  hot  for  welding. 

A  specific  kind  of  iron  is  required  for  nails,  an  important  article 
in  our  iron  works.  Nails  cut  from  charcoal  iron  are  generally  sup- 
posed to  be  of  good  quality;  still,  this  iron,  whether  from  the  char- 
coal forge  or  the  puddling  furnace,  furnishes  an  abundance  of  in- 
ferior nails.  With  respect  to  nails,  the  intrinsic  value  of  the  metal 
— that  is,  its  absolute  strength,  and  welding  properties,  as  in  the 
case  of  wire  iron — has  no  influence  whatever  upon  the  value  of  the 
manufactured  article.  All  that  is  desired  in  a  good  nail  is,  that 
it  shall  cut  smoothly,  and  bend  to  a  given  degree.  Iron  containing 
an  amount  of  foreign  matter  that  would  make  it  useless  for  any 
other  purpose,  answers  excellently.  Such  iron  may  be  manufac- 
tured from  any  kind  of  pig  metal  without  difficulty,  provided  the 
re-heating  and  heating  are  carefully  performed.  Two  different 
methods  of  manufacturing  nail  plates  are  now  practiced.  In  the 
Eastern  States,  plates  from  five  to  twelve  inches  in  width,  but  of 
no  specific  length,  are  drawn  ;  nails  are  obtained  from  cutting  these 
lengthwise.  In  the  Western  States,  it  is  customary  to  roll  sheet 
iron  from  twenty  to  twenty-four  inches  in  width,  and  six  or  seven 
19 


290  MANUFACTURE   OF   IRON. 

feet  in  length ;  and  nails  are  obtained  from  strips  cut  crosswise. 
Which  is  the  preferable  method,  it  is  not  easy  to  decide  ;  but  the 
immense  quantity  of  nails  manufactured  will  justify  us  in  giving 
the  subject  a  close  examination. 

To  make  a  nail  which  cuts  smoothly,  and  does  not  split,  we 
require  an  iron  of  very  close  grain.  For  this  purpose,  cold-short 
answers  better  than  fibrous,  particularly  coarse  fibrous,  iron.  Iron 
is  rendered  cold-short  by  carbon,  phosphorus,  and  silex ;  the  two 
latter  cannot  be  removed  by  re-heating  the  iron.  But  re-heating 
will  remove  carbon ;  and,  therefore,  when  we  take  into  considera- 
tion that  iron  which  contains  carbon  can  be  welded  with  greater 
facility,  and  by  a  lower  heat,  than  that  which  is  free  from  it,  it  is 
evident  that  a  small  amount  of  carbon  should  exist  in  the  iron  be- 
fore it  is  placed  in  the  re-heating  furnace.  From  this  it  follows 
that,  if  we  re-heat  the  iron,  and  reduce  the  size  of  the  nail-plate, 
the  iron  in  the  rough  bar  ought  to  be  cold-short :  it  will  be  fibrous 
after  it  is  reduced.  So  far  as  the  principle  of  working  it  is  con- 
cerned, this  iron  is  analogous  to  wire  iron.  The  latter  is  best 
manufactured  in  the  charcoal  forge,  or  in  the  puddling  furnace  with 
iron  boshes.  Consequently,  nail  iron  should  be  boiled  in  this  fur- 
nace, provided  it  is  repeatedly  exposed  to  a  welding  heat,  and  drawn 
out  into  small  sized  plates.  But  if  it  is  our  design  to  make  sheet 
iron,  that  is,  by  exposing  the  plates  to  the  suffocating  heat  of  a 
warming  stove,  the  iron  will  not  be  freed  from  the  carbon,  and  re- 
main cold-short.  We  th^s  see  that,  in  one  case,  small  plates  are 
advantageous,  and  in  another  case  injurious.  To  make  nail  iron 
from  white  metal,  it  is  necessary  to  work  the  latter  either  in  the 
charcoal  forge,  or  in  a  puddling  furnace  without  cooled  boshes. 
From  this  metal  good  iron  can  be  made  in  the  charcoal  forge  without 
the  least  difficulty  ;  but,  in  the  puddling  furnace  with  a  soap-stone 
or  fire  brick  hearth,  we  obtain  an  iron  of  coarse  fibre,  excellent  for 
many  purposes,  but  not  adapted  for  the  manufacture  of  nails.  If, 
in  such  cases,  we  attempt  to  leave  a  portion  of  carbon  in  the  iron, 
silex  will  remain  along  with  it,  should  not  the  pig  iron  already  have 
been  free  from  it ;  of  course,  such  iron  and  nails  will  be  cold-short, 
no  matter  by  what  method  the  iron  is  treated  after  leaving  the  pud- 
dling furnace.  Good  metal,  puddled  in  iron  boshes,  will  produce 
fibrous  iron ;  but  the  danger  is  that  it  will  lose  all  its  carbon,  and 
that,  by  repeated  heating,  a  fibrous,  dirty,  yellowish-colored,  rotten 
iron,  both  cold-short  and  hot-short,  will  result.  To  prevent  this, 
and  retain  the  fibrous  texture  of  the  puddled  bar,  it  is  preferable  to 
heat  in  stoves,  and  to  roll  sheet  iron.  This  is  the  practice  at  the 


MANUFACTURE    OF   WROUGHT   IRON.  291 

Western  iron  works,  and  is  the  result  of  necessity,  because  iron 
is  puddled  principally  from  white  metal ;  and  small  nail  plates,  ac- 
cording to  the  Eastern  fashion,  would  not  work  so  well  as  sheet  iron. 

Nail  iron  of  satisfactory  quality  can  be  easily  made,  if  we  are 
well  acquainted  with  the  process  of  puddling.  To  work  cheaply, 
we  must  resort  to  boiling.  We  may  hence  conclude  that,  in  pud- 
dling for  nail  iron,  we  require  gray  or  mottled  pig  iron,  no  matter 
of  what  quality,  provided  it  is  smelted  by  heavy  burden. 

To  secure  the  presence  of  carbon,  while  we  remove  impurities 
from  the  iron,  it  is  absolutely  necessary  to  boil  in  iron  boshes ;  and 
fine  fibrous  iron  cannot  be  made,  unless  the  pig  metal  is  fusible,  and 
remains  fusible  sufficiently  long  for  the  workman  to  wash  it  pro- 
perly in  the  cinder.  All  gray  iron  of  heavy  burden — whether 
smelted  by  charcoal,  anthracite,  or  coke,  or  whether  the  ores  con- 
tain phosphorus,  sulphur,  or  any  other  injurious  element — is  adapted 
for  this  purpose. 

We  thus  see  that  the  quality  of  bar  iron  differs  according  to  the 
different  purposes  for  which  it  is  employed.  The  blacksmith  needs 
an  iron  which  can  be  easily  welded,  which  is  neither  cold-short  nor 
hot-short.  Wire  iron  must  be  strong,  and  very  cohesive  ;  it  is  of  no 
consequence  whether  it  can  be  easily  welded,  or  whether  it  is  cold- 
short or  hot-short.  Nail  iron  may  be  hot-short,  but  its  fibre  must 
be  fine.  Railroad  iron  may  be  anything  but  cold-short.  The  pro- 
perties of  the  first  three  are  produced  by  boiling  alone.  The  latter, 
if  manufactured  in  a  cold  hearth,  will  be  imperfect. 

g.  The  elements  of  pig  iron  are  seldom  of  such  a  nature  as  to 
afford  the  exact  quality  of  wrought  iron  we  require,  and  it  need 
scarcely  be  mentioned  that,  when  smelted  from  different  ores,  it 
will  contain  admixtures  according  to  the  nature  of  the  foreign  mat- 
ter contained  in  each  ore.  A  silicious  ore  will  impart  silicon  to 
the  iron;  a  phosphate,  phosphorus;  and  sulphurets,  sulphur;  but 
as,  under  the  peculiarities  of  the  blast  furnace,  silicon  and  carbon 
have  the  greatest  affinity  for  iron,  they  are  most  constantly  associated 
with  pig  metal.  One  kind  of  metal  exerts  more  or  less  influence 
upon  another.  The  same  principle  which  we  have  observed  in  re- 
lation to  the  blast  furnace,  is  applicable  to  the  puddling  furnace ;  that 
is,  metals  of  different  quality,  mixed  together,  work  better  in  the  pud- 
dling furnace  than  metal  smelted  from  the  same  kind  of  ore.  A  metal 
from  calcareous  ore  works  far  better,  when  mixed  with  a  silicious 
metal,  than  when  mixed  with  iron  derived  from  limestone  ore;  and  if 
to  the  first  two  we  add  a  metal  smelted  from  clay  ore,  the  result  is  still 


292  MANUFACTURE   OF  IRON. 

better.      This  peculiarity  depends  less  upon  the  tendency  of  the 
foreign  matter  to  form  a  fusible  cinder,  than  upon  the  fusibility  im- 
parted indirectly  to  the  metal  by  the  foreign  matter,  and  occasioned 
by  their  mutual  affinity.     Carbon  occasions  fusibility  ;  and  silicious 
and  clay  ores  are  more  inclined  than  lime  to  make  a  carburet  of 
iron.     An  excess  of  lime  not  only  excludes  carbon,  but  it  absorbs 
sulphur  and  phosphorus.     Therefore,  the  least  fusible  iron  is  that 
smelted  by  an  excess  of  lime.     It  frequently  happens  that  a  given 
iron  is  too  fusible ;  that  it  works  slowly,  and  yields  badly.    If  to  this 
we  add  a  metal  of  a  somewhat  refractory  character,  which  also 
works  badly  by  itself,  we   shall   find  that   a  very  advantageous 
mixture  results.     In  this  way,  we  are  enabled  to  work  the  most  un- 
favorable metals  advantageously.    For  these  reasons,  it  is  advisable 
to  work  metals  from  different  localities.     In  our  attempts  to  work, 
in  a  puddling  furnace  with  iron  boshes,  coke  or  anthracite  iron,  or 
even  some  kinds  of  charcoal  iron,  we  frequently  meet  with  an  un- 
expected disappointment;  and  this  disappointment  results  from  the 
imperfect  fusibility  of  the  pig  iron  in  the  hearth  of  the  furnace.    In 
such  cases,  artificial  cinders  are  useless,  for  the  best  cinder  cannot 
reach  the  impurities.     These  are  enclosed  in  the  particles  of  iron, 
and  nothing  but  a  perfect  solution  of  the  metal  will  remove  them. 
This  solution  may  be  most  easily  effected  by  mixing  with  the  re- 
fractory iron  an  iron  that  is  very  fusible.    Admixtures  in  themselves 
injurious  cease  to  be  so  if  the  metal  can  be  perfectly  dissolved  and 
kept  liquid  until  the  cinder  has  had  sufficient  time  to  act  upon  it. 
In  proof  of  this,  it  may  be  remarked  that  phosphorus  or  sulphur 
may  be  added  as  a  flux  to  the  half  liquid  iron ;  and,  if  the  cinder 
of  the  furnace  is  of  the  proper  kind,  the  metal  manufactured  will 
be  neither  hot-short  nor  cold-short.     The  application  of  sulphur  or 
phosphorus  as  a  flux  is  difficult  and  expensive;  we  should,  therefore, 
have  recourse  to  fusible  metals.     Gray  iron  from  phosphorous,  sul- 
phurous, silicious,  and  clay  ores,  is  of  this  kind  ;  as  well  as  pig 
iron  from  the  same  ores,  smelted  by  heavy  burden.    Cinder  compo- 
sitions will  not  improve  metal  obtained  from  calcareous  ores,  or  that 
smelted  by  an  excess  of  limestone,  or  by  a  too  light  burden,  for, 
though  it  should  melt,  and  become  apparently  very  liquid,  it  will 
crystalize  so  soon  that  no  time  will  be  afforded  for  improving  it. 

In  a  previous  chapter,  we  remarked  that  the  best  policy  which  the 
iron  manufacturer  can  pursue,  is  to  make  cheap  pig  iron,  and  leave 
improvement  in  quality  to  the  puddling  furnace.  This  is  perfectly 
true  within  certain  limits.  But,  if  we  adopt  the  most  economical 


MANUFACTURE   OF   WROUGHT   IRON.  293 

plan  of  working  the  blast  furnace,  that  is,  by  carefully  preparing  the 
material,  and  by  carrying  as  heavy  a  burden  as  possible,  these  limits 
are  very  extensive.  When  these  conditions  are  observed,  good  iron 
may  be  produced  with  comparative  ease.  But  pig  iron,  from  fur- 
naces where  the  manipulations  are  carried  on  irregularly,  and  where 
a  change  of  ore,  coal,  burden,  and  workmen  often  occurs,  is  with 
difficulty  improved.  In  most  cases,  it  is  tetter  to  run  this  iron 
through  the  finery,  and  make  of  it  coarse  bar  or  railroad  iron,  than 
to  attempt  to  improve  it  in  the  puddling  furnace.  Careful  manipu- 
lation in  the  blast  furnace  is  the.  best  security  of  success  in  the 
puddling  furnace;  in  fact,  success  in  the  one  is  in  exact  proportion 
to  the  economy  observed  in  relation  to  the  other.  The  truism  that 
good  work  is  always  eventually  the  cheapest  is,  in  this  case,  amply 
confirmed. 

We  have  also  attempted  to  explain  what  kind  of  iron  can  be  made 
from  a  certain  kind  of  pig  metal,  and  to  show  what  kind  is  neces- 
sary for  specific  purposes.  So  long  as  the  process  of  puddling  is 
imperfectly  understood,  the  qualities  of  bar  iron  may  be  said  to 
depend  on  metal,  fuel,  and  labor;  for,  practically,  it  is  evident  that 
the  product  will  depend  on  the  quality  of  the  materials  we  possess. 
At  this,  if  at  any  stage,  in  the  manufacture  of  iron,  scientific  im- 
provements are  available.  Industry  and  attention  are  sufficient,  in 
most  cases,  to  produce  satisfactory  results;  but  in  puddling,  some- 
thing else  is  required.  Every  experienced  iron  manufacturer  is 
convinced  that  the  quality  and  quantity  of  iron  produced  depend 
upon  the  nature  of  the  cinder  employed.  That,  in  blast  furnace 
operations,  cinder  can  be  improved  only  to  a  very  limited  degree, 
we  have  already  shown.  But,  in  the  puddling  furnace  with  iron 
boshes,  this  improvement  may  be  indefinitely  extended. 

It  is  of  but  little  use  to  attempt  to  make  scientific  improvements 
at  the  charcoal  forge.  At  this  fire,  the  best  and  most  easy  method 
of  making  excellent  iron  is  by  employing  white  metal  of  good 
quality.  The  same  remark  is  applicable  to  the  ^puddling  furnace 
with  brick  or  soapstone  lining.  Cinder  compositions  are,  in  these 
cases,  unavailable.  These  are  of  advantage  only  in  the  puddling 
furnace  with  iron  bottom  and  boshes;  and  it  may  be  said  that  there 
would  be  no  limit  to  improvement  in  the  quality  of  iron,  if  the  iron 
lining  would  permit  of  a  heat  sufficiently  strong  to  melt  the  refrac- 
tory metals.  For  this  reason,  we  are  confined  to  metals  which  melt 
at  a  given  temperature;  and  for  this  reason,  also,  the  irregular 
nature  of  the  metal  we  employ  produces  such  unsatisfactory  results- 


294  MANUFACTURE   OF   IRON. 

The  following  statements  apply  to  furnaces  with  iron  boshes; 
though  deductions  may  be  drawn  from  them  relative  to  refining  or 
puddling. 

h.  In  puddling,  the  most  simple  method  of  improving  iron  is,  as 
we  have  previously  mentioned,  by  mixing  different  kinds  of  metal  on. 
the  same  principle  we  have  applied  at  the  blast  furnace.  The  obvious 
deduction  is,  the  more  kinds  we  mix,  the  better  the  result,  which 
coincides  exactly  with  experience.  For  this  reason,  it  is  advan- 
tageous to  mix  pig  iron  from  the  coal  regions  with  iron  smelted  from 
primitive  or  transition  ores,  and  to  mix  calcareous  metal  with  a 
silicious  or  phosphorous  pig  iron.  Stone  coal  or  coke  iron  is  greatly 
improved  by  being  mixed  with  charcoal  iron.  Baltimore  pig  iron, 
in  itself  an  excellent  iron,  would,  if  mixed  with  iron  from  Hanging 
Rock,  Ohio,  be  made  a  still  better  article.  The  latter  may  be  con- 
sidered the  best  metal  in  the  world  for  castings ;  but,  associated  with 
the  former,  it  would  make  a  very  superior  wrought  iron.  In  this 
matter,  it  is  necessary  to  guard  against  the  opinion  entertained  by 
some,  that  the  mixture  of  iron  from  different  localities  merely  is 
sufficient.  This  is  by  no  means  the  case.  Mixing  is  to  be  performed 
with  due  relation  to  the  chemical  composition  of  the  ore,  to  the  place 
at  which  the  metal  is  smelted,  and  to  the  fuel  applied  in  smelting. 
Magnetic  and  bog  ores  work  well  in  the  blast  furnace,  and  their 
respective  metals  work  well  in  the  puddling  forge.  Calcareous  ores 
and  those  containing  manganese  work  best  in  the  blast  furnace, 
if  smelted  along  with  silicious  or  clay  ores.  The  metals  derived 
from  each  of  these  ores  will  make,  when  mixed,  far  better  articles 
in  the  forge  than  each  would  produce,  if  wrought  singly. 

Another  method  of  improving  iron  is  by  mixing  the  cinders  pro- 
duced by  separate  furnaces.  This  method  is  extensively  practiced 
at  the  Western  establishments.  The  kind  employed  is  puddling 
cinder  from  furnaces  which  work  refined  metal,  and  cinder  from  char- 
coal forge  fires.  Such  cinder  is  charged  along  with  the  pig  iron  in 
the  boiling  furnace.  After  the  iron  is  melted,  hammer-slag  or  roll 
scales  are  employed  to  excite  fermentation,  as  well  as  for  the  pur- 
pose of  accelerating  the  work,  and  improving  the  quality  of  the  iron. 
The  application  of  cinders,  notwithstanding  their  unquestionable 
utility,  is  very  limited.  Inferior  pig  iron  requires  good  cinder  in 
large  quantity;  the  use  of  cinder,  therefore,  is  restricted  to  charcoal 
iron;  and  even  here  it  can  be  applied  only  in  a  very  limited  degree. 
In  this  respect,  the  Eastern  do  not  enjoy  the  advantages  which  the 
Western  works  possess,  on  account  of  the  charcoal  forges  and  char- 


MANUFACTURE    OF  WROUGHT   IRON.  295 

coal  iron  of  the  latter,  and  the  extensive  use  which  the  former 'make 
of  anthracite  pig  iron.  If  the  cinder  employed  is  of  good  quality, 
and  in  sufficient  quantity,  our  labors  cannot  fail  to  be  successful. 
But  in  the  stone  coal  regions,  good  cinder  is  not  abundant ;  and  that 
obtained  even  from  the  best  forges  is  only  of  medium  quality.  Where 
hot  blast  iron  is  refined,  it  is  so  inferior  as  to  cease  to  be  of  any  use. 
The  cinder  we  require  should  be  obtained  from  pig  iron  from  the 
richest  ores  ;  and  we  may  work  to  the  best  advantage  by  observing 
the  same  rule  in  relation  to  it  which  we  gave  relative  to  the  mixing 
of  pig  iron  and  iron  ores. 

A  better  method  of  improving  iron  than  the  application  of  cin- 
ders is  by  the  addition  of  ore  to  the  iron  charges.  This  is  exten- 
sively practiced  at  the  Eastern  works.  The  ore  is  either  put  in 
large  pieces  around  the  inside  of  the  furnace  to  protect  the  boshes, 
or  charged  in  small  fragments  with  the  metal,  like  the  additions  of 
cinder.  What  kind  of  ore  is  best  adapted  for  this  purpose  is  a  some- 
what scientific  question;  but  experience  shows  that  none  answers 
so  well  as  magnetic  ore ;  and  this  is  generally  employed.  If  mag- 
netic ores  cannot  be  obtained,  and  if  it  is  necessary  to  employ 
oxides,  or  hydrates,  it  is  advisable  to  burn  the  latter  hard,  and*  to 
convert  them  into  a  black  magnetic  oxide,  before  we  use  them. 
The  leading  principle  which  guides  us  in  the  selection  of  an  ore  is  its 
amount  of  iron  and  its  purity.  Sulphurous,  phosphorous,  and  cal- 
careous ores  will  of  course  be  rejected.  Unless  the  amount  of  iron 
in  the  ore  is  greater  than  that  in  the  cinder  we  are  making  in  the 
furnace,  we  shall  fail  to  realize  the  advantage  we  expect.  If  there 
is  more  foreign  matter  in  the  ore  than  the  cinder  generally  contains, 
we  shall  obtain  iron  in  smaller  amount,  and  of  worse  quality,  than 
though  no  ore  had  been  added.  The  best  cinder  from  charcoal 
forge  iron  contains  scarcely  more  than  eight  or  ten  per  cent,  of  fo- 
reign or  silicious  matter;  the  residue  is  iron  and  alkaline  substances. 
The  amount  of  silex  varies  from  ten  to  thirty  per  cent,  and  even 
more;  and  its  increase  beyond  ten  per  cent,  is  inversely  proportional 
to  the  quality  of  the  iron.  This  shows  clearly  what  is  required  for 
the  improvement  of  iron ;  that  is,  alkalies  and  metallic  oxides.  Al- 
kaline earths,  such  as  lime,  magnesia,  and  baryta  are  not  adapted 
for  this  composition,  because  the  temperature  of  the  puddling  fur- 
nace is  so  low  that  they  will  not  combine  with  the  silicious  matter; 
and  they  injure  the  cinder,  by  stiffening  it.  An  ore  serviceable  for 
puddling  may  contain  manganese,  clay,  soda,  potash,  and  silex ; 
but  if  it  contains  lime,  magnesia,  baryta,  sulphur,  phosphorus, 


296  MANUFACTURE   OF   IRON. 

copper,  silver,  and  more  than  twelve  per  cent,  of  silex,  it  must  be 
rejected.  The  native  magnetic  ores  are,  under  all  circumstances, 
preferable.  At  Lake  Champlain,  and  in  Essex  county,  New  York, 
an  abundance  of  suitable  ore  exists.  New  Jersey  contains  a  small 
quantity  of  ore  which,  though  very  silicious,  is  well  adapted  for  our 
purpose.  In  Missouri  and  Wisconsin,  such  an  ore  appears  to  exist 
in  abundance.  But,  in  the  anthracite  and  bituminous  coal  regions, 
the  iron  master  is  placed  in  a  somewhat  difficult  position.  The 
richest  hydrates  of  Huntingdon  or  Lebanon  county,  in  Eastern  Penn- 
sylvania, or  those  from  the  Cumberland  River,  Tennessee,  may  serve 
as  fluxes;  but  they  must  be  converted,  by  roasting,  into  magnetic 
oxides,  before  they  will  serve  for  the  improvement  of  iron.  Magnetic 
ore  of  good  quality  will,  of  course,  serve  as  well  as  hammer-slag  for 
boiling,  that  is,  for  raising  the  cinder. 

Though  the  application  of  cinder  and  iron  ore  rests  upon  sound 
principles,  it  is  still  limited  to  certain  qualities  of  metal,  and  never 
produces  anything  beyond  a  certain  kind  of  bar  iron  belonging  to 
the  cinder  we  are  able  to  generate  from  ore.  We  are  thus  some- 
times left  in  a  difficulty,  if  we  expect  a  kind  of  bar  iron  which  it  is 
beyond  the  capacity  of  our  cinder  or  ore  to  furnish  us.  In  such 
cases,  which  are  not  unfrequent,  we  should  apply  to  chemistry  for 
assistance ;  but  we  must  be  careful  not  to  waste  time  in  seeking 
that  which  it  is  not  the  province  of  chemistry  to  supply.  It  is  un- 
questionable that,  in  Pittsburgh,  iron  of  good  quality  is  produced  at 
puddling  furnaces  where  cinder  is  applied.  But  this  mode  is  so 
expensive  and  troublesome  that  it  will  be  abandoned  as  soon  as 
stone  coal  iron  is  puddled,  the  prospects  of  which  are  gradually 
brightening.  The  application  of  good  ore,  though  preferable  to 
cinder,  is  limited  to  certain  localities,  for  ore  whose  price  exceeds 
six  dollars  is  scarcely  available.  In  nearly  every  instance,  arti- 
ficial fluxes  are  the  safest  and  cheapest  of  all  fluxes,  and,  when 
intelligently  applied,  produce  results  which  we  have  yet  failed  to 
derive  from  any  cinder  or  ore. 

The  materials  suitable  for  these  artificial  compositions  are  very 
limited ;  and  their  application  requires  experience.  The  kind  of 
material  used  is  of  less  consequence,  in  the  results  obtained,  than 
the  manner  in  which  it  is  employed.  Caustic  potash,  caustic  soda, 
manganese,  iron,  and  clay  may  be  employed  with  advantage.  All 
other  matter,  even  carbonates  of  potash,  is  useless ;  lime  and  mag- 
nesia are  injurious.  Soda  is  preferable  to  potash.  We  are,  there- 
fore, reduced  to  soda,  manganese,  and  clay,  as  the  only  available 


MANUFACTURE    OF  WROUGHT  IRON.  297 

substances  not  already  contained  in  the  ore.  In  many  instances, 
pig  iron  contains  an  amount  of  manganese  which  renders  the  appli- 
cation of  any  additional  quantity  superfluous.  The  materials,  then, 
at  our  disposal — in  fact,  the  only  ones  we  need — are  soda  and  clay. 
In  some  cases,  common  salt  or  borax  is  useful.  But,  under  all  cir- 
cumstances, whatever  matter  we  employ  should  be  mixed  and 
ground  as  fine  as  possible.  Our  own  experience  has  taught  us  that, 
unless  this  is  carefully  attended  to,  success  is  somewhat  problemati- 
cal. For  this  purpose,  rotary  iron  barrels,  like  those  employed  in 
foundries  for  grinding  charcoal,  are  employed.  The  materials  are 
mixed  in  definite  proportions.  A  small  fire  is  kept  under  them  to 
dry  the  clay,  and  mix  the  soda  intimately  with  it.  The  contents  are 
then  ground  into  an  impalpable  powder,  which  must  then  be  placed 
in  a  dry,  warm  place  for  preservation.  When  moist,  even  though 
under  the  influence  of  a  dry  atmosphere,  its  virtues  are  greatly 
diminished.  To  illustrate  the  operation  of  artificial  fluxes,  we  shall 
relate  our  own  experience  in  regard  to  the  different  kinds  of  pig 
iron  for  which  they  were  employed,  and  indicate,  as  we  proceed,  the 
various  compositions  which  we  tested.  We  shall  present,  at  first, 
the  most  simple  cases,  and  gradually  ascend  to  those  which  are  more 
complex. 

1.  Metals  smelted  by  charcoal  from  phosphurets.  It  is  imma- 
terial to  what  degree  this  iron  may  be  cold-short,  provided  it  is 
mottled  or  gray  pig,  or  the  result  of  heavy  burden.  By  a  judi- 
cious application  of  Shafhseutl's  compound — that  is,  five  parts  of 
common  salt,  three  of  manganese,  and  two  of  clay — it  will  produce 
an  excellent  bar  iron,  equal  to  any  iron  from  the  best  charcoal 
metal.  The  clay  alluded  to  is  not  a  silicious,  sandy,  white  matter, 
or  common  loam ;  but  the  finest  white  plastic  clay,  which,  when 
wet,  is  very  tough,  and  when  dry,  of  smooth  appearance ;  it  forms 
an  impalpable  powder.  The  pig  iron  is  heated  as  in  common  ope- 
rations. It  is  melted  down  by  a  rapid  heat ;  the  damper  is  closed  ; 
and  the  cinder  and  metal  diligently  stirred.  In  the  mean  time,  the 
above  mixture,  in  small  parcels  of  about  half  a  pound,  is  introduced 
in  the  proportion  of  one  per  cent,  of  the  iron  employed.  If,  after 
this,  the  cinder  does  not  rise,  hammer-slag  may  be  applied.  Where 
competent  workmen  are  employed,  a  good  furnace  will  make  a  heat 
in  two  hours,  and  furnish  highly  satisfactory  results.  Where  the 
operation  is  well  conducted,  there  will  be  neither  too  much  nor  too 
little  cinder  in  the  furnace.  From  a  rolling-mill  of  which  we  have 
personal  knowledge,  containing  six  double  furnaces,  not  even  a 


298  MANUFACTURE   OF   IRON. 

wheelbarrowful  of  cinder  was  carried  away,  while  no  cinder,  in 
addition  to  the  roll  scales,  and  the  cinder  supplied  by  the  furnaces, 
was  added.  - 

2.  Pig  iron,  from  sulphurous  ore  and  heavy  burden,  smelted  by 
charcoal.     The  appearance  of  this  metal  is  very  black.     Under 
ordinary  circumstances,  it  produces  very  red-hot  iron.     It    was 
melted  and  wrought  by  the  same  method  as  No.  1,  with  this  differ- 
ence, that,  instead  of  clay,  chalk  was  employed.     In  the  furnace,  it 
worked  somewhat  faster  than  the  above,  but  always  produced  an 
iron  inferior  to  it. 

3.  Gray  charcoal  iron,  of  any  cast  or  mottled  iron,  will  produce 
with  great  facility,  by  working  it  in  the  same  way  as  No.  1,  a 
superior  fibrous  iron  ;  but  great  industry  is  required  to  make  as  fine 
and  strong  an  article  as  No.  1. 

4.  Gray  anthracite  iron,  if  free  of  sulphur,  requires  the  mixture 
of  No.  1  ;  but  if  it  contains  any  trace  of  sulphur,  No.  2  will  answer 
better.    This  remark  also  applies  to  gray  coke  iron.    But  coke  iron  is 
less  easily  wrought  into  a  good  article  than  anthracite  iron.  Neither 
works  so  well  as  charcoal  pig.     The  main  difficulty  in  working  them 
consists  in  melting-in.     But,  by  careful  and  industrious  manipula- 
tion, we  shall  arrive  at  as  satisfactory  results  as  with  charcoal  iron. 

5.  From  white  iron  of  small  burden,  or  from  an  excess  of  lime- 
stone or  manganese,  it  is  useless  to  attempt  to  produce  a  good  ar- 
ticle.    A  small  amount  of  such  iron,  containing  phosphorus  or  sul- 
phur, will  make  a  whole  charge  cold-short,  or  hot-short,  and  it  is 
impossible  to  remove  silex  from  it.    By  the  addition  of  a  very  small 
portion  of  soda  and  clay,  the  better  kinds  of  such  iron  may  be  ad- 
vantageously puddled.     If  caustic  soda  is  not  too  expensive,  it  may 
be  considered  preferable  to  common  salt.     One  pound  of  soda  and 
one  pound  of  clay  are  sufficient  for  500  pounds  of  iron ;  or,  if  caustic 
soda  is  not  applied,  two  pounds  of  common  salt.     All  inferior  and 
irregular  metals,  whether  charcoal,  anthracite,  or  coke  iron,  should 
be  sent  to  the  refinery,  melted  into  finery  metals,  and  puddled  in 
furnaces  with  brick  or  soapstone  lining,  in  which  operation  a  small 
addition  of  clay  and  soda  will  be  found  advantageous.     From  these 
demonstrations,  we  see  of  what  importance  pig  iron,  which  melts 
and  keeps  liquid  for  a  given  length  of  time,  is  to  puddling  establish- 
ments.    Such  iron  is  produced  only  by  blast  furnaces  which  carry 
heavy  burden  and  consume  a  very  limited  amount  of  fuel. 

i.  In  puddling  manipulations,  we  must  be  careful  that  the  fur- 
nace hearth  is  kept  tight,  and  that  the  cinder  does  not  leak  through 
the  bottom  even  in  the  strongest  heat.  A  heat  which  loses  its  cin- 


MANUFACTURE    OF  WROUGHT   IRON.  299 

der  is  spoiled.  The  quality  and  quantity  of  the  metal  are  inju- 
riously affected.  The  amount  of  cinder  required  in  the  furnace 
depends  upon  the  metal  we  use,  upon  the  competency  of  the  work- 
men, and  upon  the  iron  we  design  to  make.  Good  puddlers  will 
work  to  advantage  with  a  small  quantity;  but  poor  workmen  re- 
quire an  abundant  supply.  With  a  small  quantity,  the  work  is  ac- 
celerated. Inferior  requires  more  cinder  than  good  pig  iron,  and 
gray  more  than  white.  If  we  desire  strong  iron,  of  fine  fibre,  we 
must  employ  gray  pig  of  a  fusible  nature.  By  diligent  work,  with- 
out adding  any  scales  or  hammer-slag  to  the  mixture,  No.  1  will 
furnish  an  iron  of  unsurpassable  absolute  strength. 

If  we  desire  to  make  wire  iron,  it  is  necessary  to  employ  gray 
pig  containing  a  large  amount  of  carbon,  and  flux  it  by  means  of 
caustic  soda  and  clay.  If  expense  is  no  object,  borax  may  be  em- 
ployed with  even  greater  advantage.  In  this  instance,  a  fine-grained 
iron,  of  steel  fracture,  but  softer  than  steel  and  harder  than  fibrous 
iron,  is  required.  Fibrous  iron  is  not  adapted  for  the  manufac- 
ture of  wire.  It  does  not  draw  well,  and  is  not  so  strong  as  iron 
of  a  fine-grained  nature.  Such  iron  should  be  free  from  impurities 
and  cinder ;  for  these  not  only  weaken  it,  but  make  the  wire  short 
and  unclean,  besides  working  hard  on  the  draw-plate.  To  remove 
these  impurities,  we  require  a  very  alkaline,  but  at  the  same  time 
very  fusible,  cinder.  Such  a  cinder  will  make  a  fine  compact  iron, 
exhibiting  no  fibres  in  the  rod  or  billet,  but  only  in  small  wire. 

Jc.  The  height  of  the  furnace  top,  or  arch,  from  the  bottom,  varies, 
according  to  circumstances,  from  eighteen  to  thirty  inches.  In 
puddling  furnaces,  from  eighteen  to  twenty-four  inches  ;  and  in 
boiling  furnaces,  from  twenty-two  to  thirty.  The  latter  is  the  ex- 
treme, and  seldom  applied.  Inferior  pig  iron  which  melts  easily, 
and  keeps  liquid,  requires  a  higher  arch  than  pig  iron  of  good  quality. 
Gray  metal  produces  better  iron  by  a  high  than  by  a  low  top.  White 
metal  of  any  kind  works  more  favorably  by  a  low  arch,  for' which 
reason  it  is  puddled,  and  not  boiled.  A  high  arch  works  more 
slowly  and  consumes  more  fuel  than  a  low  arch,  but  the  yield  is 
superior  both  in  quantity  and  quality.  Wire  iron  requires  a  strong 
heat,  but  a  high  top.  Good  puddlers  will  work  with  a  low  arch ; 
but  such  an  arch  cannot  be  intrusted  to  inferior  workmen. 

I.  The  depth  of  the  bottom,  that  is,  the  iron  bottom  below  the 
door-plate  or  cinder-plate,  is  as  variable  as  the  roof.  From  four  to 
six  inches  is  sufficient  in  a  puddling,  and  from  six  to  twelve  in  a  boil- 
ing furnace.  In  some  cases,  the  latter  is  rather  too  great  a  depth; 


^300  MANUFACTURE    OF   IRON. 

and  eleven  inches  may  be  considered  the  extreme.  A  deeper  hearth 
is  required  for  bad  than  for  good  pig  iron.  A  deep  bottom  con- 
sumes more  fuel,  and  requires  greater  attention,  than  a  flat  bottom, 
but  it  makes  better  iron,  and  yields  it  in  larger  quantity.  A  large 
body  of  cinder  does  not  make  very  fibrous,  but  very  clean  iron. 

m.  The  dimensions  of  the  grate  of  a  puddling  furnace  depend 
upon  the  size  of  the  hearth,  and  upon  the  kind  of  fuel  employed. 
For  wood,  in  small  chips,  a  grate  whose  size  is  in  the  ratio  of  one 
foot  to  twelve  feet  of  hearth,  is  sufficiently  large ;  for  bituminous 
coal  like  that  of  the  Pittsburgh  vein,  one  foot  to  four.  For  hard 
and  impure  coal,  it  may  be  extended  to  half  the  size  of  the  hearth. 
But  where  blast  is  applied,  as  in  the  case  of  Pennsylvania  anthra- 
cite, these  rules  must,  in  some  measure,  be  modified.  However,  if 
we  have  any  doubt  about  the  matter,  it  is  better  to  make  the  grate 
too  large  than  too  small.  The  only  disadvantage  of  a  large  grate  is 
that  it  consumes  a  greater  amount  of  fuel  than  one  of  the  proper  size. 

n.  The  influence  of  fuel  upon  the  quality  of  the  iron  manu- 
factured is  not  remarkable;  but,  in  some  instances,  it  is  important. 
Sulphur  and  phosphorus  do  not  appear  to  have  any  influence  what- 
ever upon  the  iron  in  the  furnace,  for  we  have  experienced  no  dif- 
ficulty in  puddling  with  sulphurous  coal  or  turf,  the  latter  of  which 
generally  contains  phosphorus  in  admixture.  Wood  undoubtedly 
affects  the  process  very  favorably.  We  have  observed  very  closely 
two  establishments  in  which  the  same  kind  of  metal  was  puddled 
by  wood  and  by  inferior  anthracite;  the  abilities  of  the  workmen 
about  equal.  The  iron  puddled  by  wood  was  strong,  white,  and  of 
fine  fibre.  That  puddled  by  anthracite  was  equally  strong,  but  dark 
in  the  fracture,  and  of  coarse  fibre.  In  the  blacksmith's  fire,  the 
superiority  of  the  former  was  still  more  apparent.  The  only  reason 
which  can  be  assigned  for  this  difference  is  the  difference  in  the 
composition  of  the  ashes  of  the  wood  and  anthracite.  Wood  ashes 
are  of  an  alkaline,  the  ashes  of  anthracite  are  of  an  acid,  nature. 
With  wood  or  bituminous  coal  no  difficulty  is  experienced  in  pud- 
dling, on  account  of  the  ashes  ;  but  with  anthracite,  the  ashes  have 
at  times  proved  a  serious  obstacle.  The  application  of  blast,  and 
the  use  of  large  grates  in  the  modern  anthracite  furnace,  have,  in  a 
great  measure,  removed  this  obstacle.  Anthracite  iron,  though 
sufficiently  strong  and  malleable,  is  frequently  of  so  dark  a  color  as 
to  be  unfavorable  for  blacksmith's  use.  This  color  is  imparted  by 
the  ashes  carried  over  from  the  grate  upon  the  hearth.  These 
ashes,  which  are  not  pure  earth  and  silex,  contain  a  large  amount 


MANUFACTURE    OF  WROUGHT  IRON.  301 

of  carbon.  If  they  cover  the  surface  of  the  exposed  iron,  carbon 
will  be  inclosed  in  the  balls.  The  silex  is  then  absorbed  by  the 
protoxide  of  iron,  and  a  black  cinder  is  formed  ;  when,  to  this,  black 
carbon  is  added,  it  is  not  strange  that  the  iron  becomes  dark  in  the 
fracture.  The  most  effectual  preventives  of  this  are  quick  work, 
and  an  abundance  of  very  fusible  cinder.  Still,  it  may  be  stated, 
as  a  general  rule,  that  iron  puddled  by  a  small  amount  of  cinder, 
and  by  the  application  of  stone  coal,  no  matter  of  what  kind,  is  of 
dark  fracture.  If  more  cinder  is  applied,  the  same  pig  iron  will 
exhibit  a  brighter  fracture. 

o.  Heating  stoves  attached  to  puddling  furnaces  are,  where 
fuel  is  expensive,  and  where  competent  workmen  are  employed, 
a  valuable  appendage.  By  their  use,  a  quarter  of  an  hour  or  more 
is  saved  each  heat.  If  the  same  wages  are  paid,  with  or  without 
stoves,  it  is  advantageous  to  employ  them,  because  the  time  saved 
by  their  use  may  be  profitably  employed  in  improving  the  quality 
of  the  iron,  or,  if  this  is  satisfactory,  in  working  inferior  metal. 
Where  they  are  used,  it  is  advisable  to  give  the  metal  only  a  cherry 
red  heat,  and  to  keep  it  in  the  stove  as  short  a  time  as  possible. 
The  best  situation  for  a  stove  is  between  the  pillars  of  the  stack. 
This  is  common  at  the  New  England  works,  where  the  flue  is 
made  narrower  than  usual,  to  keep  the  heat  more  in  the  furnace 
hearth.  In  Europe,  many  varieties  of  such  stoves  are  in  operation. 
At  Pittsburgh,  and  throughout  the  West,  no  use  is  made  of  them, 
for  there  fuel  is  cheap  beyond  comparison,  and  the  metal  employed 
works  so  fast  that  hurried  manipulation  is  unnecessary.  But  when 
our  Western  friends  shall  be  obliged  to  abandon  the  running-out 
fire,  and  shall  be  compelled  to  boil  their  iron,  the  application  of 
stoves  will  be  necessary ;  not  for  the  saving  of  fuel,  but  for  the  saving 
of  time.  This  will  be  particularly  the  case  where  a  large  body  of 
hot  blast  iron  is  to  be  wrought,  for  this  generally  works  very  slowly. 
Stoves  designed  to  heat  the  pig  iron  beyond  a  cherry  red  heat,  or 
even  to  melt  it,  are  not  advantageous  in  the  way  of  appendages. 

p.  At  the  Eastern  establishments,  wages  for  boiling  vary  from 
three  dollars  and  fifty  cents  to  four  dollars  per  ton  ;  the  latter  for 
anthracite  coal  and  for  anthracite  pig.  At  the  West,  six  dollars 
per  ton  are  paid  for  boiling  and  five  for  puddling — helpers'  wages 
included. 

q.  The  yield  depends  very  much  on  the  nature  of  the  metal,  and 
upon  the  mode  of  working  it.  In  puddling  good  white  metal,  there 
is  a  loss  of  four  or  five  per  cent.  With  bad  white  metal  the  loss  is 


302  MANUFACTURE    OF   IRON. 

twenty  per  cent.,  and  even  more  where  we  seek  to  improve  its  quality. 
Gray  pig  metal,  of  whatever  quality,  may,  by  a  judicious  applica- 
tion of  ore  and  artificial  fluxes,  be  made  to  yield  from  ninety-five 
to  ninety-eight  per  cent,  of  rough  bars  per  100  cent,  of  metal. 

VIII.   Creneral  Remarks  on  Refining. 

Our  present  run-out  fire — finery — is,  as  we  have  previously  re- 
marked, an  imperfect  apparatus.  Its  design  is  to  improve  the 
quality  of  pig  metal,  and  to  diminish  the  labor  of  converting  it  into 
wrought  iron.  This  design  is  partly  accomplished ;  but  the  ap- 
paratus is  still  far  from  being  complete.  It  is  not  our  object,  at 
present,  to  suggest  any  improvement  upon  it,  but  simply  to  define 
its  purpose,  and  to  exhibit  its  imperfections. 

At  the  time  coke  iron  was  first  made,  a  large  quantity  of  bad 
iron  was,  as  might  have  been  expected,  produced  in  the  blast  fur- 
nace. Such  metal,  of  course,  worked  well  neither  in  the  charcoal 
forge  nor  in  the  puddling  furnace.  In  such  a  case,  but  little  could 
be  expected  from  the  run-out  fire  ;  because  then  the  nature  of  the 
charcoal  forge  and  of  the  puddling  and  blast  furnaces  was  not  well 
understood.  But  this  offset  to  imperfect  results  cannot  now  be  so 
successfully  pleaded  by  the  manufacturer.  Gray  pig  iron  from  a 
well-conducted  blast  furnace  operation  can  be  puddled  to  the  best 
advantage,  without  refining ;  and  it  is  generally  admitted  that  such 
iron  is  of  superior  quality.  In  addition  to  this,  experience  shows 
that  it  is  cheaper  than  refined  iron.  Therefore  the  only  iron  left 
for  refining  is  that  which  results  from  badly-conducted  blast  fur- 
nace operations.  That  the  run-out  fire  is  not  the  best  apparatus 
for  effecting  that  result,  is  sufficiently  proved  by  experience ;  but, 
theoretically,  the  fact  may  easily  be  demonstrated. 

If  ore  is  once  reduced  to  iron,  the  result  may  be  a  very  imperfect 
metal.  Still  the  largest  amount  of  matter  in  it  is  iron.  In  the 
crude  metal,  it  is  seldom  less  than  ninety  per  cent.  This  element 
is,  in  all  instances,  the  same ;  it  is  as  favorable  in  bad  as  in  the 
finest  metal,  with  the  exception  of  being  adulterated  by  some  ad- 
mixtures which,  under  certain  circumstances,  are  injurious.  If  such 
metal  has  been  properly  treated  in  the  blast  furnace,  we  find  no 
difficulty  in  producing  from  it  a  good  wrought  iron.  But  if  badly 
managed,  it  is  almost  impossible  to  obtain  this  result.  The  abun- 
dance of  bad  iron  in  the  market  is  a  proof  that  the  finery  accom- 
plishes but  a  slight  improvement.  The  main  difficulty  in  working 
pig  metal  smelted  by  a  high  heat  in  the  blast  furnace  consists, 


MANUFACTURE    OF  WROUGHT  IRON.  303 

as  we  have  before  explained,  in  the  impossibility  of  so  completely 
dissolving  it  as  to  enable  the  cinder  to  act  upon  the  foreign  matter  in 
it  to  advantage.  In  most  instances,  it  readily  dissolves  by  a  tolerable 
heat;  but  the  cohesion  of  its  particles  is  so  great,  and  its  affinity  for 
oxygen  so  strong,  that  it  does  not  remain  liquid  sufficiently  long  for 
the  removal  of  its  impurities.  The  objections  made  against  cold 
boshes  in  the  puddling  furnace  apply  with  greater  force  against  the 
finery  fire,  for  in  the  latter  cold  boshes  not  only  exist,  but  are  in  a 
less  advantageous  form  than  in  the  double  puddling  furnace.  There- 
fore, the  finery  fire  eifects  scarcely  any  improvement  in  the  quality 
of  iron,  and  is,  of  course,  not  adapted  to  produce  cheap  work. 

The  chief  purpose  of  the  run-out  fire  is  the  manufacture  of  a 
more  uniform  metal  than  is  produced  by  the  blast  furnace.  By 
bringing  the  metal  to  a  somewhat  uniform  quality,  we  are  enabled 
to  secure  more  regular  manipulation  both  in  the  forge  and  in  the 
mill.  But  this  advantage  can  be  arrived  at  in  a  more  perfect  man- 
ner by  very  different  methods.  Another  advantage  it  is  said  to  pos- 
sess is,  that  it  does  not  consume  so  much  iron,  in  neutralizing  the 
silex  of  the  pig  metal,  as  the  puddling  furnace.  This  is  true  ;  but 
if  the  run-out  fire  works  by  coke,  which  is  generally  the  case,  all 
the  ashes  of  the  fuel  are  saturated  by  iron,  and  a  large  quantity  of 
the  sand  which  forms  the  bottom  of  the  fire.  These  objections  are  of 
a  practical  nature.  We  know  that  it  is  vain  to  attempt  to  improve 
radically  bad  metal  by  running  it  through  the  finery.  We  know, 
further,  that  this  is  not  the  method  of  making  cheap  iron.  The 
finery  fire  will  waste  from  six  to  fifteen,  and  even  twenty  per  cent, 
of  metal.  We  may  say  that  ten  per  cent,  of  this  is,  on  an  average, 
uselessly  lost ;  for,  in  the  puddling  furnace,  we  can  produce  a  yield 
equal  to  that  in  the  finery,  whether  the  metal  is  refined  or  not.  This 
loss — without  considering  the  wages  of  workmen,  from  one  dollar  to 
one  dollar  and  fifty  cents,  and  the  expense  of  fuel,  which  for  coke 
is  seventy-five  cents,  and  for  charcoal  two  dollars  and  fifty  cents — 
amounts  to  four  dollars  per  ton  of  iron,  that  is,  if  we  estimate  the 
iron  at  but  two  cents  per  pound.  The  expenses  of  refining,  there- 
fore, in  the  most  favorable  case,  amount  to  at  least  five  dollars  and 
a  half  per  ton. 

Pig  iron  which  it  is  impossible  to  improve  effectually  in  the  pud- 
dling furnace  will  always  be  manufactured.  Besides,  it  is  necessary 
to  puddle  iron  for  railroad  and  heavy  bar  iron.  For  this  purpose, 
we  need  white  plate  metal.  For  the  manufacture  of  this  article, 
we  require  an  apparatus  superior  to  any  we  at  present  possess — an 


304  MANUFACTURE  OF  IRON. 

apparatus  more  in  accordance  with  the  advancement  which  science 
has  made  in  all  of  its  various  departments.  In  the  following 
pages,  we  shall  endeavor  to  point  out  still  more  completely  than 
heretofore  the  deficiencies  of  the  run-out  fire;  and  for  the  purpose 
of  assisting  inventive  genius,  we  shall  add  the  different  methods  of 
refining  at  present  practiced  in  various  parts  of  the  world: — 

a.  1.  By  charging  to  excess,  in  the  blast  furnace,  ores  containing 
phosphorus;  these  will  produce  white  metal  with  the  least  injurious 
admixtures.  2.  By  casting  the  pig  iron  directly  from  the  blast  furnace 
in  iron  moulds,  and  cooling  it  suddenly  by  a  current  of  cold  water. 
3.  By  running  the  re-melted  iron  into  a  mass  of  cold  water.  4.  By 
the  making  of  rosettes,  practiced  in  Styria,and  described  in  Chapter 
III. — an  effectual  method,  unless  the  metal  is  very  bad.  5.  By 
tempering  the  metal;  this  is  done  by  exposing  it  for  twelve  or  twenty- 
four  hours  to  a  cherry  red  heat.  6.  By  refining  the  iron  in  the 
blast  furnace  before  tapping  ;  this  is  effected  by  turning  the  blast 
upon  the  hot  iron,  and  in  this  way  burning  impurities  and  carbon. 
7.  By  feeding  good  ore,  hammer-slag,  or  wash  iron  at  the  tuyere. 
Wash  iron  is  the  fine  grains  of  iron  gathered  by  pounding  the  fur- 
nace cinder,  and  washing  it  in  a  current  of  water;  the  water  car- 
ries off  the  sand  of  the  cinder,  and  the  grains  of  iron  left  amount, 
in  many  instances,  to  six  or  seven,  seldom  less  than  three  or  four, 
per  cent,  of  the  cinder.  This  method  is  extensively  practiced  in 
Western  Germany,  where  poor  silicious  ores  are  smelted.  8.  By 
melting  the  pig  iron  in  the  common  charcoal  forge,  and,  by  chilling 
it  in  water,  preparing  it  for  the  following  operation.  A  division  of 
labor  is  thus  practiced  in  the  same  apparatus :  9.  By  melting  the 
pig  iron  in  a  reverberatory  furnace,  and  by  blowing  upon  it,  as 
practiced  in  this  country  and  elsewhere  ;  or  by  washing  the  melted 
metal  with  ore,  hammer-slag,  or  other  ingredients,  to  make  it 
white.  Of  all  the  methods  described,  of  all  that  are  known,  none 
is  so  well  adapted  to  improve  iron  as  the  puddling  furnace.  The 
most  useful  in  the  above  enumeration  is  the  refining  of  the  iron 
in  the  blast  furnace  before  it  is  let  out ;  but  this  method  is  not 
generally  applicable,  and  it  would  not  answer  at  all  in  an  anthra- 
cite furnace. 

A  method  of  improving  iron,  commonly  employed,  is  by  imme- 
diately cooling  the  hot  metal  in  iron  moulds,  or  by  the  application 
of  water.  Generally,  both  means  are  resorted  to  in  the  same  case. 
As  far  as  the  removal  of  impurities  is  concerned,  no  improvement 
is  effected;  for  the  iron  contains  as  much  silex,  carbon,  and  sul- 


MANUFACTURE   OF  WROUGHT  IRON.  305 

phur  after  it  is  chilled,  as  before.  Still,  the  manipulation  is  pro- 
ductive of  great  advantage.  We  shall  endeavor,  in  a  future  page, 
to  explain  the  nature  of  this  curious  process.  Metal  designed  for 
the  forge  should  be  cast  in  iron  moulds,  if  for  no  other  purpose 
than  to  keep  it  free  from  sand. 

Of  late  years,  attempts  have  been  made  to  remove  impurities  by 
galvanizing  iron ;  but  such  experiments  are  so  scientific  as  to  be 
productive  of  no  practical  utility.  What  may  be  done,  is  not 
always  profitable  in  business.  We  do  not  depreciate  the  motive 
power  of  electricity ;  but  we  must  be  permitted  to  doubt  that  it 
can  successfully  compete  against  the  steam-engine,  so  far  as  economy 
is  concerned. 

IX.   Theory  of  Refining  and  Puddling. 

We  now  proceed  to  the  examination  of  a  subject  which  is  no 
less  difficult  than  interesting.  It  unfolds  to  us  the  nature  of  the 
material  with  which  we  have  to  deal,  and  shows  us  to  what  extent 
we  can  succeed  in  improving  the  quality  of  metal  by  converting  it 
into  wrought  iron.  We  shall  probably  succeed  in  conveying  a  bet- 
ter understanding  of  this  subject,  by  pointing  out  the  nature  of  pig 
iron  and  wrought  iron. 

a.  The  chemical  difference  between  cast  iron  and  wrought  iron 
consists  principally  in  the  difference  of  degree  in  which  foreign 
matter  is  present  in  each  ;  which  is  in  larger  amount  in  the  former 
than  in  the  latter.  'We  should  be  cautious  not  to  infer  that  this  rule 
is  universally  true ;  that  is,  by  applying  it  to  iron  from  different 
sources.  This  rule  is  applicable  only  to  a  given  cast  iron,  and  to 
the  wrought  or  bar  iron  which  is  made  from  it.  There  are  many 
cases  in  which  wrought  iron  contains  a  larger  amount  of  impurities 
than  cast  iron,  and  yet  is  malleable ;  while  cast  iron  of  the  same 
composition  may  be  very  hard  and  brittle.  Berzelius,  a  celebrated 
Swedish  chemist,  tells  us  that  he  detected,  in  a  certain  kind  of  bar 
iron,  eighteen  per  cent,  of  silex;  and  that  this  iron  was  still  mal- 
leable and  useful.  One-tenth  of  that  amount  of  silex  will  make 
cast  iron  brittle.  The  foreign  matters  generally  combined  with 
pig  iron  are  carbon,  silicon,  silex,  sulphur,  phosphorus,  arsenic, 
zinc,  manganese,  titanium,  chrome,  aluminium,  magnesium,  and 
calcium.  Each  of  these  tends  to  make  iron  brittle.  Therefore,  in 
converting  cast  into  wrought  iron,  it  is  necessary,  as  far  as  possible, 
to  remove  them.  Carbon,  and,  as  far  as  we  can  judge,  all  other 
foreign  matter,  divide  the  crude  iron  into  two  very  distinct  classes. 
20 


306  MANUFACTURE    OF  IRON. 

In  the  one,  carbon  is  only  an  accidental  mechanical  admixture;  in 
the  other,  it  is  in  definite  chemical  combination  with  the  iron.  To 
the  former  belong  the  white  iron  of  heavy  burden,  and  gray  iron; 
to  the  latter  the  white  iron  of  small  burden,  or  very  fusible  ores. 
Judging  from  the  behavior  of  the  different  metals  in  the  refining 
and  puddling  process,  we  are  inclined  to  believe  that  the  presence 
of  silicon  and  silex  has  a  similar  influence,  for  it  is  almost  impos- 
sible to  remove  silex  from  white  metal  with  which  carbon  is  chemi- 
cally combined.  The  silex  is  present  very  probably  in  the  form  of 
silicon.  This  accounts  for  the  great  difficulty  of  improving  such 
metal  by  any  refining  process.  The  same  remarks  apply  to  phos- 
phorus and  sulphur.  White  metal  of  small  burden  may  contain 
from  five  to  nearly  six  per  cent,  of  carbon  ;  and,  if  smelted  from 
poor  ore,  almost  an  equal  amount  of  other  foreign  matter,  such  as 
silicon.  Upon  the  presence  andform  of  these,  its  white  color  and  crys- 
talization,  in  a  great  degree,  depend.  Gray  pig  iron  seldom  contains 
more  than  4.75  per  cent,  of  carbon,  and  generally  only  from  3.50 
to  4  per  cent.  When  carbon  is  present  to  the  amount  of  but  two 
to  three  per  cent.,  it  becomes  white.  We  know,  from  experience, 
that  white  iron  of  heavy  burden  behaves  well,  and  that  it  can  be 
greatly  improved  in  the  puddling  furnace ;  but  with  less  facility  in 
the  charcoal  forge.  We  also  know  that  it  is  almost  impossible  to  im- 
prove white  iron  of  poor  origin,  and  light  burden,  containing  carbon 
in  large  amount,  by  any  method  of  manipulation.  If  the  presence  of 
carbon  were  the  only  difficulty  to  be  overcome,  we  should  not  de- 
spair of  working  it  advantageously.  In  fact,  the  better  kinds  of  this 
metal  are  worked  with  success  in  the  charcoal  forge ;  but  in  this 
forge  the  poorer  kinds  will  not  work  at  all.  In  the  puddling  fur- 
nace, the  former  will  produce  a  good  article,  though  not  equal  to 
gray  metal  from  the  same  ore  ;  but  the  latter  will  yield  a  very  infe- 
rior iron.  Hence  we  conclude  that,  in  this  metal,  silex  is  present  in 
the  form  of  silicon,  and  that  it  is  chemically  combined  with  the  metal 
as  an  alloy.  This  remark  also  applies  to  calcium  and  phosphorus. 
By  these  combinations,  the  difficulties  encountered  in  our  attempts 
to  remove  impurities  from  metal,  are  explained.  Were  carbon  the 
only  difficulty  against  which  we  have  to  contend,  the  metal  could 
be  made  to  work  well  in  any  apparatus.  Were  the  protoxide  of  iron 
the  only  alkali  in  the  cinder,  this  of  itself  would  absorb  any  amount 
of  oxidized  silicon  or  silex.  But,  in  consequence  of  the  reduction 
of  silex  to  silicon,  the  latter  must  first  absorb  oxygen ;  and  this  it 
can  absorb  only  from  the  protoxide  of  iron  in  the  cinder.  The 


MANUFACTURE  OF  WROUGHT  IRON.  307 

silex,  thus  forming,  will  attract  three  atoms  of  iron  in  absorbing 
oxygen.  The  oxygen,  in  turn,  will  form  very  adhesive  white 
iron,  which  crystalizes  rapidly.  Its  crystals  include  carbon, 
silicon,  and  even  silex.  In  this  instance,  we  require  a  far  larger 
amount  of  oxygen  to  remove  impurities  than  in  the  case  of  gray 
iron  ;  and  this  oxygen  can  be  derived  only  from  the  oxygen  of  the 
cinder,  or,  what  is  the  same  thing,  from  the  protoxide  of  iron  which 
the  cinder  contains;  or,  where  the  cinder  is  very  alkaline,  from  mag- 
netic oxide  of  iron.  Hence  it  follows  that,  to  saturate  the  silex 
formed,  an  immense  quantity  of  iron  is  taken  from  the  metal  itself, 
to  be  oxidized  by  the  atmospheric  air.  This  oxidation  raises  the 
temperature  of  the  metal,  and  separates  the  carbon  before  the  re- 
maining impurities  can- be  effectually  removed.  The  only  method 
of  improving  such  metal  is  to  melt  it  by  a  very  high  heat,  and 
under  cover  of  a  very  strong  alkaline  cinder.  But  this  is  not  feasi- 
ble either  in  the  charcoal  forge  or  in  the  puddling  furnace. 

b.  In  composition,  wrought  iron  is  frequently  inferior  to  the  metal 
from  which  it  is  made;  that  is,  if  we  apply  the  term  inferior  to  the 
preponderance  of  foreign  matter  which  it  contains.  Wrought  iron 
containing  a  large  amount  of  silex  and  carbon,  especially  the  first, 
and  even  a  given  proportion  of  phosphorus,  may  still  be  a  good 
bar  iron.  The  main  difference  between  pig  and  wrought  iron  con- 
sists in  their  mechanical  structure  or  aggregate  form.  Pig  iron  is 
a  homogeneous  mixture  of  impurities  and  metal,  in  which,  by 
affinity,  atom  is  brought  close  to  atom,  and  in  which  a  transforma- 
tion from  the  mechanical  to  a  chemical  admixture  is  easily  effected, 
as  in  the  case  of  gray  and  white  metal.  Wrought  or  bar  iron  is  a 
mixture  of  iron  more  or  less  pure  with  a  mass  of  homogeneous  im- 
purities, or  cinder — the  latter  filling  the  crevices  between  the  crys- 
tals of  the  iron.  If  we  remember  that  iron  is  fusible  in  proportion  to 
the  carbon  it  contains,  we  shall  arrive  at  a  very  comprehensive  con- 
clusion. If  we  melt  metal  or  pig  iron,  and  expose  the  cinder  which 
surrounds  it  to  the  influence  of  oxygen,  the  carbon  will  evaporate, 
and  iron  of  greater  or  less  purity  will  remain.  This  iron,  to  be 
kept  liquid,  requires  a  higher  temperature  than  at  first;  conse- 
quently, unless  the  temperature  is  raised,  it  will  crystalize.  In 
this  state  of  metamorphosis,  its  infusibility  will  increase,  and  after 
the  expulsion  of  the  carbon,  it  will  contract  into  a  solid  mass  by 
the  highest  possible  heat.  By  stirring  and  mixing  the  pasty  iron, 
small  crystals  are  formed ;  at  first,  on  account  of  the  partial  fusing 
of  the  iron,  in  small  particles ;  but,  as  the  fusibility  diminishes, 


308  MANUFACTURE    OF  IRON. 

these  particles  unite  by  force  of  cohesion;  and  the  bodies  thus 
formed  may,  by  exposure  to  a  higher  heat,  be  welded  together. 
The  mixing  of  cinder  and  iron  will  prevent  the  latter  from  forming 
large  crystals.  This  result,  of  course,  will  be  more  easily  prevented 
by  diligent  than  by  tardy  manipulation.  Where  the  pig  iron  is  of 
such  a  nature  as  to  keep  liquid  while  the  work  goes  on  slowly,  still 
better  results  will  be  afforded.  This  process  is  analogous  to  that 
of  salt-boiling,  in  which,  by  stirring  the  brine,  the  formation  of  large 
crystals  is  prevented.  If  the  crystals  of  iron  thus  formed  cohere, 
they  form,  under  the  influence  of  motion,  a  porous,  spongy  mass, 
whose  crevices  are,  if  not  filled,  at  least  coated,  with  cinder.  If 
these  masses,  which  are  the  loups  or  balls  at  the  charcoal  forge  and 
puddling  furnaces,  are  shingled  or  squeezed,  the  crystals  of  iron 
will  not  unite,  but  form  coated  cells  with  a  film  of  cinder,  of  greater 
or  less  thickness,  according  to  the  fusibility  of  the  cinder.  Iron  in 
a  connected  form,  and  cinder  in  separate  cells,  are  thus  blended  in 
a  homogeneous  mass.  The  more  this  iron  is  stretched,  the  more  it 
forms  fibres.  Fibrous  bar  iron  resembles  hickory  wood,  in  the  fact 
that  it  is  a  combination  of  fibres  and  spaces.  In  bar  iron,  these  spaces 
are  filled  with  cinder.  When  other  circumstances  are  equal,  the 
strength  of  the  iron  will  be  proportional  to  the  fineness  of  the  fibres. 
That  portion  of  the  iron  which  is  not  melted,  which  crystalizes  too 
fast,  or  whose  premature  crystalization  the  workman  cannot  pre- 
vent, is  in  the  condition  of  cast  metal,  and  cannot  be  converted  into 
fibrous  wrought  iron.  In  the  puddling  furnace,  it  is  necessary  to 
prevent  crystalization  by  manual  labor.  This  result,  whether  in 
the  Catalan  forge,  the  wiilfs  oven,  or  the  German  forge,  is  partly 
accomplished  by  the  blast. 

If  the  characteristic  difference  between  wrought  and  pig  iron 
consists  in  nothing  else  than  such  a  well-regulated  mechanical  mix- 
ture of  cinder  and  iron,  we  ought  to  be  enabled  to  produce  fibrous 
wrought  iron  from  any  cast  iron,  whether  it  is  or  is  not  purified  by 
the  process  we  have  described.  This  is  actually  the  case.  Very 
fibrous  bar  iron,  which  is  strong  and  malleable,  is  made  from  very 
inferior  metal  in  which  no  removal  of  its  impurities  is  effected. 
Among  other  instances,  which,  we  may  observe,  are  very  frequent, 
in  which  this  result  is  accomplished,  we  may  mention  that,  at 
Hyanges,  France,  very  inferior  metal  is  converted,  by  a  cheap  and 
skillful  puddling  process,  into  a  very  fibrous  bar  iron,  of  great 
strength  and  ductility.  But  this  iron  is  puddled  and  re-heated  by  the 
lowest  possible  heat ;  it  is  then  rolled,  and  ready  for  market.  For 


MANUFACTURE    OF  WROUGHT   IRON.  309 

hoops,  rails,  and  nails,  it  is  a  very  useful  article;  but  it  is  of  no  use 
to  the  blacksmith.  Heated  by  any  temperature  beyond  that  of  the 
puddling  and  re-heating  furnaces,  it  returns  to  its  primitive  state, 
in  which  condition  it  becomes  worse  than  the  cast  iron  from  which  it 
was  originally  made.  None  but  a  very  skillful  blacksmith  can  weld 
it ;  for,  when  slightly  re-heated,  it  falls  to  coarse,  sandy  pieces,  or 
melts  like  pig  iron.  That  which  thus  loses  its  fibrous  texture  in 
heating,  the  smith  calls  burnt  iron. 

c.  Fibrous  iron  returns  in  this  manner  to  its  original  condi- 
tion because  of  the  impurities  which  exist  in  it;  these  absorb 
oxygen.  It  is  of  little  consequence  whether  such  impurities  are 
carbon,  silicon,  or  calcium,  for  each  of  these  will  reduce  the  cinder. 
Let  us  assume  that  carbon  is  present  in  fibrous  bar  iron.  If  we 
heat  this  iron  to  a  certain  temperature,  the  carbon  which  it  contains 
will  combine  with  the  protoxide  of  iron  in  the  cinder,  and  form  iron 
and  carbonic  oxide.  The  latter  escapes,  and  leaves  silex  in  the 
pores  of  the  iron.  The  silex,  thus  enclosed,  will  not  prevent  the 
cohesion  of  the  crystals  into  an  aggregated  mass.  This  mass  is 
then  in  the  same  form  as  crude  iron.  Silicon  acts  in  the  same  way 
as  carbon,  and  so  does  any  element  which  has  more  affinity  for 
oxygen  than  iron.  Therefore,  the  destruction  by  heat  of  the  fibres 
in  iron  is  nothing  else  than  the  result  of  the  destruction  of  the  cin- 
der, which,  by  its  vitreous  nature,  prevented  the  formation  of  larger 
crystals  in  the  iron.  The  sudden  cooling  of  such  iron  will  produce 
the  same  result. 

Wrought  iron  of  a  white  color,  fine  fibre,  and  yielding  when 
struck  a  dead  sound,  is  not  liable  to  these  alterations.  It  remains 
fibrous  under  all  conditions,  and  is  altered  neither  by  heat  nor 
water ;  that  is,  provided  the  heat  is  not  excessive,  or  of  too  long 
duration.  Such  iron  must  be  free  of  all  carbon  or  elementary  im- 
purities, or  its  cinder  must  be  of  such  a  nature  as  not  to  be  altered 
by  carbon  or  silicon.  In  Styria  and  Carinthia,  iron  of  good  weld- 
ing properties,  very  fibrous,  and  remaining  fibrous,  however  often  it 
is  heated  or  cooled,  and  very  tenacious — in  fact,  a  perfect»sample  of 
excellent  iron — is  manufactured  from  carbonaceous,  spathic  ores, 
which  contain  a  large  amount  of  manganese.  Bar  iron,  from  what- 
ever source,  if  manufactured  from  metal  smelted  by  a  well-con- 
ducted process  from  ore  containing  manganese,  is  generally  of  the 
same  character ;  at  least,  it  is  always  the  best  for  blacksmith's  use. 
These  facts  show  conclusively  that  manganese  has  a  favorable  influ- 
ence upon  iron.  Manganese  has  greater  affinity  for  oxygen  than 


310  MANUFACTURE   OF   IRON. 

iron;  and  its  oxides  are  powerful  bases,  stronger  even  than  the  oxides 
of  iron.  If  cinder,  composed  of  manganese  and  silex,  is  that  which 
produces  the  fibre  in  the  iron,  carbon  will  have  but  little  influence 
upon  the  cinder,  for  manganese  is  reduced  to  metal  only  under  very 
favorable  conditions.  It  is  with  still  more  difficulty  separated  from 
silex.  If  the  destruction  of  fibres  in  bar  iron  be  thus  prevented, 
it  is  evident  that  a  stronger  alkali  would  be  still  more  favorable. 

d.  The  removal  of  carbon  from  pig  iron  is  of  less  consequence 
than  the  removal  of  silex  and  other  foreign  matter  from  it.  The 
first  may  be  effected  with  comparative  facility,  as  is  proved  by  the 
case  we  have  related  in  which  iron  from  the  purest  plate  metal  was 
converted  into  black  magnetic  oxide.  In  that  case,  the  plate  iron 
contained  at  least  five  per  cent,  of  carbon;  but  it  was  so  totally 
destroyed  that  the  heat  of  the  re-heating  furnace  converted  the 
iron  into  an  oxide  of  iron.  This  shows  clearly  that  the  very  exist- 
ence of  iron  depends  upon  the  presence  of  a  given  amount  of  car- 
bon; otherwise,  the  iron,  when  exposed  to  heat,  will  absorb  oxygen 
into  its  minutest  particles.  Analyses  prove  that  the  best  kinds  of 
wrought  iron  contain  from  1.2  to  1.4  per  cent,  of  carbon,  in  addi- 
tion to  sulphur,  phosphorus,  silicon,  manganese,  arsenic,  and  tita- 
nium. The  two  last  elements  are  frequently  found  in  Swedish 
iron,  and  generally  in  iron  manufactured  from  magnetic  ore.  Of 
all  these  substances,  silex,  phosphorus,  and  sulphur  are  with  the 
greatest  difficulty  removed;  and,  when  present  in  too  large  quan- 
tity, those  only  which  so  injure  the  metal  as  to  make  their  removal 
necessary.  If  they  are  combined  in  an  oxidized  state  with  the 
pig  iron,  they  may  be  removed  with  but  little  difficulty.  But  this 
is  not  the  case  with  phosphorus  and  sulphur,  for,  in  the  presence  of 
the  large  amount  of  carbon  which  exists  in  the  blast  furnace,  phos- 
phurets  and  sulphurets  are  formed;  and  these  are  mixed  with  the 
metal.  We  know  positively  that  silicon  may  exist  in  an  oxidized 
form  in  the  metal.  Silex,  generally  in  admixture  with  ore,  is  re- 
duced to  silicon  only  by  a  very  favorable  heat.  Very  strong  cohe- 
sion alone  will  form  a  chemical  compound  of  iron,  silicon,  and  car- 
bon. This  state  of  things  appears  to  exist  at  the  blast  furnace, 
where  fusible  ores  are  smelted  by  an  excess  of  coal,  want  of  pres- 
sure in  the  blast,  blast  of  too  great  pressure,  hearth  of  too  great 
width,  and  imperfectly  prepared  ores.  From  such  operations,  we 
obtain  pig  iron  which  is  with  difficulty  improved;  whence  we  con- 
clude that  the  injurious  impurities  so  difficult  of  removal  are  chemi- 
cally combined  with  the  iron. 


MANUFACTURE   OF  WROUGHT   IRON.  311 

e.  Carbon  can  exist  in  iron  in  two  distinct  combinations.  It  is 
mechanically  mixed  with  the  gray  pig,  and  chemically  with  the 
white  iron  of  small  burden ;  the  former  contains  it  in  smaller  amount 
than  the  latter.  We  know  less  of  silex.  We  know  that  the  metal 
contains  silex,  but  of  the  form  in  which  it  is  present,  whether  as 
silicon,  or  its  oxide,  silex,  we  are  ignorant.  Iron,  carbon,  and  sili- 
con have  a  great  affinity  for  each  other,  but,  so  far  as  we  can  judge, 
it  requires  a  given  temperature  and  certain  conditions  to  develop  a 
polarity  sufficiently  strong  to  blend  them  so  intimately  together  that 
the  specific  quality  of  each  is  lost  in  that  of  the  other.  This  is  actu- 
ally the  case  between  carbon  and  iron ;  and  it  is  rational  to  expect 
that  it  is  the  case  between  silicon  and  iron,  as  well  as  between  iron, 
phosphorus,  and  sulphur.  The  two  latter  combine  with  iron  at 
almost  any  temperature.  If  such  a  chemical  connection  between 
silicon  and  carbon  happens  to  exist  in  metal,  it  is  evident  that  their 
separation  must  be  a  matter  of  extreme  difficulty.  Silicon  has  a 
stronger  affinity  for  oxygen  than  either  carbon  or  iron ;  for  this  rea- 
son, as  well  as  for  the  large  amount  of  oxygen  required  to  oxidize 
the  silicon,  it  is  so  difficult  to  remove  it  from  the  iron. 

The  amount  of  carbon  may  be  very  large  in  some  kinds  of  metal, 
particularly  those  smelted  from  poor  silicious  ore,  or  those  smelted 
by  coke  and  anthracite,  or  the  result  of  light  burden.  If  such 
metal  is  re-melted  in  a  puddling  furnace,  or  in  any  apparatus  ia 
which  there  is  access  of  atmospheric  air,  the  silicon  will  absorb 
oxygen,  should  it  exist.  If,  perchance,  atmospheric  oxygen,  or, 
what  is  still  worse,  watery  vapors  have  access  to  the  metal,  the 
temperature  of  the  particles  of  iron  is  raised  to  such  a  height  that  a 
portion  of  carbon  will  evaporate.  The  metal,  thus  transformed, 
will,  by  its  infusibility,  enclose  portions  of  metal  which  are  brittle. 
The  fibres  of  such  iron  we  cannot  expect  to  retain.  If  present 
in  the  rough  bars,  they  will  disappear  when  the  iron  is  re-heated. 
This  result,  theoretically  deduced,  coincides  with  practical  observa- 
tions. The  fast  working  of  such  metal,  when  it  is  to  be  wrought  in 
the  charcoal  forge,  may  be  retarded  by  throwing  sand  on  the  par- 
tially refined  iron.  Sand  dissolves  a  part  of  the  iron  which  encloses 
the  injurious  particles,  by  forming  with  it  cinder ;  and  gives  the  en- 
closed iron  a  fusible  protection.  It  also  retards,  in  the  mean  time, 
the  too  rapid  absorption  of  oxygen.  Such  iron,  of  course,  yields 
badly  in  the  forge  fire  ;  the  wrought  iron  which  is  produced  from  it 
will  be  inferior.  Metal  so  impure  should  never  be  taken  to  the 
charcoal  forge.  In  the  puddling  furnace,  it  is  worked  with  but 


312  MANUFACTURE    OF   IRON. 

little  advantage,  though  with  greater  success  than  in  the  charcoal 
forge.  As  previously  remarked,  puddling  furnaces  with  cooled 
boshes  are,  in  this  case,  of  no  use ;  for  this  metal  requires  a  high 
heat,  and  a  large  quantity  of  cinder,  to  make  it  work  slowly,  to 
protect  the  iron  and  carbon,  and  gradually  to  oxidize  the  silicon. 
When  it  is  worked  by  the  addition  of  oxidizing  cinders,  or  of  water; 
or  when  it  is  melted  slowly  ;  or  where  oxygen  has  access  to  it, 
which  happens  if  there  is  too  small  an  amount  of  coal  in  the  grate, 
the  result  is  a  bad  article,  and  a  poor  yield. 

In  our  investigations,  we  invariably  fall  back  upon  the  white 
metal  containing  carbon  in  large  amount.  But  when  we  consider 
its  frequent  appearance  in  the  forges,  its  bad  qualities,  the  fact  that 
it  originates  from  an  imperfect  blast  furnace  manipulation,  and, 
finally,  its  relation  to  hot  blast,  we  hope  we  shall  be  justified  in 
this  course  by  the  intelligent  reader.  In  fact,  this  subject  affords 
the  best  illustration  of  the  theory  of  refining. 

Besides  the  white  metal,  composed  of  iron,  carbon,  and  silicon, 
which  may  result  from  the  very  best  ores,  as  is  the  case  in  the  mag- 
netic ore  regions,  there  is  white  iron,  with  an  admixture  of  phos- 
phorus and  sulphur.  The  latter  is  inferior  even  to  the  former,  if  the 
result  of  light  burden.  But  the  worst  of  all  metals  is  that  smelted 
from  bad  ores,  and  from  an  excess  of  limestone,  and  hot  blast.  In 
addition  to  carbon,  silicon,  phosphorus,  and  sulphur,  which  may  be 
removed,  this  metal  contains  calcium  and  magnesium,  the  elements 
of  alkalies,  which  destroy  every  prospect  of  improvement  with  the 
means  at  present  at  our  disposal.  As  we  cannot  entirely  get  rid  of 
this  metal ;  as  its  quality  is  of  such  a  nature  as,  thus  far,  to  have 
baffled  the  most  acute  ingenuity ;  and  as  it  contains  at  least  eighty- 
five  or  ninety  per  cent,  of  good  iron,  we  trust  that  the  time  will 
not  be  considered  entirely  lost  which  we  shall  consume  in  a  some- 
what close  examination  of  the  subject.  This  may  serve  to  suggest 
a  method  of  improving  it,  or  of  preventing  the  production  of  so 
large  an  amount  of  it  as  heretofore. 

/.  All  metal  smelted  beyond  a  certain  temperature,  and  produced 
under  specific  conditions,  is  white ;  often  of  a  bluish  color,  if  it  con- 
tains the  elements  of  the  alkaline  earths.  We  suppose  that  the 
earthy  matters,  silex,  lime,  and  magnesia,  are  reduced  to  metals, 
and  chemically  combined  with  the  iron.  If  we  rnelt  such  iron  with 
access  of  oxygen,  it  will  of  course  be  transformed  into  a  pasty 
mass,  because  a  part  of  it  is  not  fusible,  that  is,  already  deprived  of 
carbon,  for  this  is  the  only  means  which  can  effectually  secure  fusi- 


MANUFACTURE   OF  WROUGHT  IRON.  313 

bilitj.  Silicon  and  calcium  increase  the  fusibility  of  metal ;  but 
these  are  oxidized  by  the  slightest  exposure,  and  thus  serve  to 
diminish  its  fusibility,  and  in  this  way,  as  well  as  by  the  increase 
of  temperature  resulting  from  oxidation  in  the  metal  itself,  destroy 
the  carbon.  If  the  carbon  could  be  retained,  it  would  tend  to  keep 
the  metal  liquid ;  it  would  thus  offer  a  chance  of  acting  upon  the 
impurities.  For  these  reasons  such  metal  will  work  fast,  unless 
we  are  desirous  of  improving  its  quality,  which,  with  the  better 
kinds  of  charcoal  metal  from  rich  ore  and  judicious  blast  furnace 
manipulations,  is  generally  our  object.  But  when  we  attempt  to 
improve  its  quality,  the  metal  works  slowly,  yields  very  poorly,  and 
is  seldom  or  never  made  to  produce  an  article  of  tolerable  value. 
We  know,  practically,  the  difficulties  connected  with  such  metal, 
and  from  facts  we  have  presented,  have  deduced  a  rational  theory, 
•which,  if  judiciously  applied,  ought  to  show  in  what  direction  our 
attempts  at  improvement  should  tend.  If,  in  consequence  of  oxi- 
dation, the  metal  becomes  less  fusible,  and  thus  encloses  impurities, 
a  mechanical  separation — that  is,  fast  work  and  the  application  of 
strong  cinder,  the  latter  of  which  will  keep  the  iron  separate — 
ought  to  be  a  means  of  improvement.  Such  is  actually  the  case. 
By  the  application  of  strong  cinder  where  silex  predominates,  a  dark 
fibrous  bar  iron  is  produced,  which,  when  re-heated,  returns  to  a  more 
or  less  strong  cast  iron,  that  is,  a  cold-short  bar  iron  of  a  crystaline 
or  granular  fracture.  This  kind  of  puddling  is  very  frequently 
practiced,  especially  in  our  anthracite  region ;  but  that  which  most 
clearly  illustrates  such  work  is  the  puddling  process  at  Hyanges, 
to  'which  we  have  so  often  referred.  At  that  place,  the  pig  iron  is 
melted-in  with  a  mixture  of  feldspar  and  squeezer  cinder;  in  this 
the  iron  keeps  pasty  for  a  long  time.  By  means  of  the  feldspar, 
cinder  of  a  silicious  composition  is  formed  which  is  very  fusible  ; 
before  the  feldspar  is  melted,  it  is  almost  sandy.  Its  fusibility  in- 
creases as  the  furnace  becomes  warmer,  and  as  the  work  progresses. 
"When  its  fusibility  arrives  at  a  point  at  which  its  utility  appears 
questionable,  the  cinder  is  let  off,  and  the  iron,  by  this  time  ready 
for  shingling,  is  quickly  balled  up,  and  taken  to  the  hammer.  In- 
ferior pig  iron  may  thus  be  worked  to  advantage ;  but  its  quality 
cannot  be  much  improved.  In  this  case,  we  see  by  what  means  a 
fibrous  iron  can  be  produced  from  a  metal  which,  to  all  appear- 
ances, it  is  impossible  to  improve.  But,  at  the  same  time,  it  sug- 
gests the  method  by  which  improvements  may  be  effected.  It 
shows  that  an  alkaline  cinder  is  of  no  advantage  in  working  such 


314  MANUFACTURE   OF   IRON. 

iron.  As  the  removal  of  silicon  or  silex  is  the  principal  object  at 
which  we  aim,  the  correctness  of  the  method  pursued  in  working 
white  iron  is  somewhat  doubtful ;  nevertheless,  it  is  the  best  with 
which  we  are  acquainted. 

g.  Metal  whose  quality  is  such  as  either  to  produce,  if  worked 
on  a  cheap  plan,  bad  iron,  or  to  produce  it  in  such  limited  quantity 
as  to  make  its  application  unprofitable,  is  said  to  be  the  result  of 
too  much  heat  in  the  blast  furnace,  or  the  effect  of  hot  blast.     Low 
temperature  and  cold  blast  do  not  make  such  iron,  or,  at  least,  not 
very  frequently.     Therefore,  the  cause  of  the  difficulty  lies  chiefly 
in  the  conditions  of  the  blast  furnace.     Before  hot  blast  was  intro- 
duced, such  pig  iron  was  generally  the  consequence  of  too  wide  a 
hearth.   When  it  happened  to  be  smelted,  the  furnace  was  blown  out, 
and  a  new  hearth  put  in.    In  this  case,  the  cause  of  bad  iron  must  be 
attributed  to  the  absence  of  free  oxygen  in  the  hearth,  as  well  as  to 
an  excess  of  fuel.    Where  cold  blast  is  employed,  gray  iron  is  made 
in  a  high,  narrow  hearth,  and  flat  boshes;  but  where  hot  blast  is  used, 
it  can  be  made  in  a  low  hearth,  and  steep  boshes.     Consequently, 
in  the  latter  case,  the  heat  is  high  up  in  the  stack,  for  which  reason 
the  pig  iron  will  contain  a  large  amount  of  chemically  combined 
impurities,  and  will  become  hard  and  brittle;,     Therefore,  hot  blast 
does  not  affect  the  iron  in  any  other  way  than  it  is  affected  by  cold 
blast  and  too  wide  a  hearth.     It  is  thus  evident  that  the  conclusion 
•which  most  writers  on  this  subject  have  arrived  at,  that  a  too  high 
temperature  is  the  only  cause  of  the  inferiority  of  the  metal,  needs 
qualification.     That  is  to  say,  if,  where  the  hearth  is  too  wide,  and 
the  boshes  too  sloping,  the  same  kind  of  metal  is  produced  by  cold 
blast  which,  under  other  conditions,  is  produced  by  hot  blast,  the 
conclusion  that  an  excessive  temperature  occasions  the  bad  metal 
referred  to,  is  obviously  erroneous.     From  this  argument,  which 
holds  good  in  many  other  respects,  we  infer  that  chemical  composi- 
tions of  iron  and  impurities  are  the  result  of  conditions  in  which  free 
oxygen  is  excluded  from  acting  upon  the  metal.     This  explains 
at  once  the  necessity  of  the  differences  in  the  construction  of  blast 
furnaces  for  different  ore  and  fuel.     For  gray  pig  iron,  or  pig  iron 
in  which  impurities  and  iron  are  mechanically  mixed,  a  narrow 
hearth  is  required.     On  what  hypothesis  can  we  explain  the  fact 
that  silex,  in  this  case,  is  not  reduced,  and  that  carbon  is  not  more 
closely  connected  with  the  rnetal  ?     Not  on  that  of  a  want  of  heat, 
for  the  heat  is  more  concentrated  in  a  narrow  than  in  a  wide  hearth. 
The  only  way  of  accounting  for  so  singular  a  fact  is,  either  that  the 


MANUFACTURE   OF  WROUGHT  IRON.  315 

melted  metal  is  prevented,  for  want  of  time,  from  chemically  com- 
bining with  silex  and  carbon,  or  that  such  a  combination,  already 
existing,  is  destroyed  by  free  oxygen.  Against  the  first  hypothesis, 
we  may  urge  the  fact  that  a  too  wide  hearth  forms  chemical  combi- 
nations ;  for  in  a  wide  hearth  less  time  is  allowed  for  the  iron  to 
come  down  than  in  a  narrow  hearth.  In  support  of  the  latter  hypo- 
thesis, we  may  adduce  the  result  of  our  experience  in  the  manufac- 
ture of  steel.  German  steel  is  manufactured  from  white  metal 
simply  by  melting  it  down  in  a  charcoal  forge.  It  may  be  made 
with  the  greatest  facility,  though  of  inferior  quality,  in  a  very  hot 
puddling  furnace.  In  this  case,  the  very  best  kind  of  metal  is  re- 
quired; but  this  will  not  affect  our  argument.  The  steel  metal  is 
iron  and  carbon  chemically  combined,  and  the  steel  itself  iron  and 
carbon  mechanically  combined.  By  re-melting  the  metal,  with  the 
observance  of  certain  practical  rules,  the  chemical  combination  is 
destroyed.  In  this  instance,  we  see  that  it  is  not  an  excessive 
temperature  which  produces  inferior  white  iron.  It  is  a  heat  rela- 
tively too  high,  under  given  circumstances.  These  circumstances 
appear  to  be  the  too  rapid  conversion  of  the  oxygen  of  the  blast 
into  carbonic  oxide,  or  the  passing  of  the  reduced  ore  or  metal 
before  the  tuyere  under  conditions  in  which  it  is  either  not  touched 
at  all,  or  touched  in  very  slight  degree,  by  the  blast.  Too  high  a 
tuyere  in  the  blast  furnace  is  also  very  apt  to  produce  such  metal. 
In  the  chapter  on  hot  blast,  we  shall  make  some  additional  remarks 
on  this  subject. 

From  the  foregoing,  we  may  draw  the  conclusion  that  white 
metal,  chemically  combined  with  impurities,  is  produced  under 
circumstances  imperfectly  understood;  and  that  this  chemical  com- 
bination, by  re-melting  the  metal,  and  carefully  observing  certain 
practical  rules,  can  be  dissolved,  and  changed  into  a  mechanical 
admixture.  How  the  metal  is  made  in  the  blast  furnace,  is  a 
matter  about  which  we  may  be  indifferent.  The  only  question 
which  concerns  us  is,  how  to  improve  it.  That  such  metal  can  be 
converted  into  steel,  is  an  evidence  that  it  can  be  improved;  but 
this  conversion  involves  a  greater  expense  of  fuel  than  bar  iron 
which  is  made  from  the  same  metal  will  justify.  In  the  former 
case,  a  high  heat,  and  the  presence  of  carbon,  are  all  that  is  neces- 
sary to  dissolve  the  chemical  connection  of  the  compounds.  In 
such  metal,  designed  for  steel,  but  little  silex  is  generally  found, 
for  it  is  made  from  the  richest  ores.  Where  a  large  amount  of 
silex  is  to  be  removed,  the  case  is  different. 


316  MANUFACTURE   OF   IRON. 

We  would  not  devote  so  much  space  to  the  consideration  of  this 
metal,  were  it  not  so  common  an  article.  If  there  existed  a  method 
of  improving  it,  it  would  be  still  more  common ;  but,  until  lately, 
this  has  been  difficult.  It  is  not  the  object  of  this  work  to  propose 
improvements,  the  results  of  which  may  be  doubtful.  All  such 
matters  we  consign  to  the  enterprise  of  the  industrious  manufac- 
turer, who  does  not  despair  after  the  failure  of  an  experiment.  But 
we  may  be  permitted  to  point  out  here  the  leading  principles  which 
such  improvements  must  necessarily  embody.  A  high  heat  is  re- 
quired to  dissolve  the  chemical  combination  of  iron  and  foreign 
matter.  A  limited  amount  of  heat  and  oxygen  is  sufficient  to  re- 
move carbon  from  this  combination.  In  the  removal  of  silicon, 
carbon  and  oxygen  are  needed;  otherwise  the  iron  becomes  in- 
fusible. If  calcium  and  magnesium  are  mixed  with  the  iron 
— which,  however,  is  seldom  the  case — the  difficulties  which  we 
encounter  are  so  grave  that  we  may  safely  say,  with  the  means  at 
present  at  our  service,  that  the  improvement  of  the  metal  is  an 
impossibility. 

h.  The  rule,  that  cinders  are  the  criterion  of  the  quality  of  the 
iron  made,  is  in  no  instance  more  correct  than  in  the  present  case. 
The  removal  of  impurities,  of  which  silex  and  silicon  are  the  most 
injurious,  is  the  main  object  in  the  refining  of  iron.  Inasmuch  as 
the  principles  of  refining  are  the  same,  whatever  is  the  substance 
"with  which  we  may  be  engaged,  we  shall  confine  our  attention 
principally  to  silex.  To  remove  silex,  which  is  an  acid,  we  re- 
quire an  alkali  with  which  to  combine  it,  and  thus  to  form  a 
vitrified,  fusible  slag.  The  greater  the  affinity  in  the  slag  for 
silex,  the  greater  the  amount  of  silex  which  will  be  removed. 
Therefore,  in  a  forge  cinder,  we  need  as  much  alkali  as  we  can 
possibly  obtain,  for  upon  the  quantity  and  quality  of  this  will  de- 
pend the  quality  of  the  iron.  Forge  cinder  from  a  charcoal  fire 
contains  more  alkali  than  cinder  from  the  puddling  furnace.  This 
accounts,  in  some  measure,  for  the  difference  in  the  quality  of  iron 
which  each  produces.  On  close  examination,  we  shall  find,  in  this 
circumstance,  the  reason  why  the  charcoal  forge  will  not  work  in- 
ferior metals  to  advantage,  and  why  the  puddling  furnace  does  not 
produce  from  good  metal  an  article  equal  to  that  from  the  charco-al 
forge.  The  reason  is  evident.  Metals  containing  a  large  amount 
of  silex  must,  if  we  desire  a  good  article,  necessarily  be  partially 
converted  into  cinder;  because  good  cinder  requires  a  given  amount 
of  protoxide  of  iron  to  neutralize  the  silex  which  it  contains.  If 


MANUFACTURE   OF  WROUGHT  IRON.  317 

the  silex  is  not  thus  neutralized,  the  iron  will  be  worse  than  the 
same  metal  from  the  puddling  furnace ;  because,  in  addition  to 
silex,  we  leave  more  carbon  in  the  iron,  on  account  of  the  presence 
and  contact  of  charcoal.  This  makes  the  iron  in  the  charcoal  forge 
more  cold-short  than  that  in  the  puddling  furnace.  Intrinsically, 
it  may  be  purer,  but  it  is  not  generally  more  useful.  In  conse- 
quence of  its  bricks  and  coal  ashes,  consisting  almost  exclusively 
of  silex,  the  puddling  furnace  cannot  produce  so  good  a  cinder  as 
the  charcoal  forge,  in  which  everything  can  be  kept  free  of  silex. 
Therefore,  the  puddling  furnace  makes  better  iron  from  poor  metal 
than  the  charcoal  forge  ;  but  the  latter  makes  better  iron  than  the 
former  from  good  metal. 

To  what  extent  the  qualities  of  iron  are  connected  with  the  com- 
position of  cinder  may  be  understood  by  comparing  one  cinder  with 
another.  From  a  rolling-mill  in  Firmy,  France,  a  puddling  cinder 
contained  31.2  silex,  60.5  protoxide  of  iron  and  manganese,  and 
1.7  phosphorus.  In  this  case,  we  observe  an  immense  quantity  of 
protoxide  of  iron  compared  to  that  contained  in  blast  furnace  cinder. 
We  also  observe  a  diminution  of  silex,  besides  a  large  portion  of 
phosphorus.  Puddling  cinder  from  Dowlais,  Wales,  consisted  of 
36.8  silex,  61.0  protoxide  of  iron,  and  1.5  clay  or  alumina.  The 
first  cinder  is  from  charcoal  pig  iron  ;  the  latter  from  coke  iron.  Re- 
heating furnace  cinder  contains  about  40  or  50  per  cent,  of  silex, 
and  often  clay,  in  proportion  to  the  sand  used  in  making  the  hearth. 

Charcoal  forge  cinder  from  a  forge  where  good  iron,  though  on  a 
cheap  plan,  is  manufactured — Hartz  Mountains,  Germany — con- 
tained 32.3  silex,  62.0  protoxide  of  iron,  1.4  magnesia,  2.6  prot- 
oxide of  manganese,  and  0.28  potash. 

The  amount  of  protoxide  of  iron  increases,  and  that  of  silex  de- 
creases, in  proportion  to  the  quality  of  the  iron.  A  cinder  from  a 
good  iron  in  France  consisted  of  16.4  silex,  79.0  protoxide  of 
iron,  3.0  lime,  1.2  alumina,  and  0.6  protoxide  of  manganese.  A 
Swedish  cinder,  from  the  softest  kind  of  iron,  was  composed  of  7.60 
silex,  82.10  protoxide  of  iron,  2.80  magnesia,  1.10  alumina,  and 
6.80  protoxide  of  manganese.  And  a  cinder  from  a  strong  kind  of 
Swedish  bar  iron  was  composed  of  38.5  silex,  44.4  protoxide  of 
iron,  3.1  lime,  3.1  alumina,  and  11.0  protoxide  of  manganese. 

From  these  analyses  of  cinder,  we  deduce  a  leading  principle 
which  will  guide  us  in  directing  the  refining  operations.  The  in- 
crease of  alkalies  in  the  cinder  shows  the  method  by  which  we  must 
arrive  at  a  good  result.  But  it  is  necessary  to  guard  against  the 


318  MANUFACTURE   OF   IRON. 

very  natural  conclusion  that  the  iron  will  be  improved  in  proportion 
to  the  increase  of  alkali  in  the  cinder.  This  is  not  the  case,  at  least 
so  far  as  the  strength  of  the  iron  is  concerned.  As  before  explained, 
wrought  iron  is  nothing  else  than  cast  iron  with  a  judicious  admix- 
ture of  cinder.  If  that  cinder  is  of  such  a  nature  as  to  be  decom- 
posed by  the  remaining  carbon,  or  other  unoxidized  impurities,  the 
fibrous  bar  iron  will  return  to  cast  iron,  on  being  re-heated. 

Therefore,  the  absolute  cohesion,  or  strength,  of  wrought  iron,  is 
not  dependent  upon  the  degree  of  purity  of  the  metal,  but  upon  a 
given  mixture  of  cinder  and  iron.  Pure  iron,  .which  is  always  soft, 
may  be  required  for  various  purposes — as,  for  example,  in  the 
manufacture  of  cast  steel ;  but,  in  most  cases,  an  impure,  but 
fibrous  iron  is  preferable.  In  making  wrought  iron,  the  main  diffi- 
culty consists,  not  in  producing  fibres  in  the  first  stages  of  the  ope- 
ration, for  this  may  be  accomplished  by  almost  every  experienced 
manufacturer,  but  in  retaining  these  fibres  through  every  subse- 
quent stage  of  the  operation.  We  do  not  think  it  necessary  to 
enter  upon  an  investigation  relative  to  the  proof  of  our  statement 
that  the  absolute  strength  of  iron  does  not  consist  in  its  purity,  but 
in  its  aggregate  form.  Nobody  will  doubt  that  a  fine  thread  of  the 
worst  iron  is  stronger  than  an  equally  fine  thread  of  glass.  Yet  how 
elastic  is  such  a  thread  of  glass  !  Who  doubts  that,  if  all  the  fibres 
of  a  hickory  stick  were  united  in  one  solid  mass,  without  pores,  the 
absolute  strength  of  the  stick  would  be  greatly  diminished  ?  at  least 
that  its  strength  would  be  far  inferior  to  a  bar  of  iron  of  poor 
quality  ?  Yet  how  far  superior  is  the  fibrous  hickory  to  cold-short 
iron,  with  respect  to  relative  strength  and  elasticity  !  But  it  is 
unnecessary  to  dwell  upon  so  plain  a  subject. 

i.  To  form  bar  iron  of  a  permanent  fibrous  structure,  the  cinder 
employed  must  be  of  such  a  nature  as  to  resist  the  reducing  influence 
of  carbon  and  other  unoxidized  compounds  of  iron.  Forge  cinder 
is  chiefly  composed  of  protoxide  of  iron.  One  reason  of  this  is 
that  it  is  the  nearest  alkali  at  hand.  Another  is  that  the  protoxide 
of  iron,  and  the  silex  separated  from  the  iron,  are  approximate  at 
the  moment  of  liberation,  and,  according  to  general  laws,  combine 
more  readily  than  they  would  if  once  separated.  Protoxide  of  iron 
is,  under  ordinary  circumstances,  with  difficulty  reduced  to  iron, 
particularly  if  once  in  chemical  connection  with  silex  ;  but  its  re- 
duction is  possible,  as  is  proved  by  the  reduction  of  forge  cinder  in 
the  charcoal  forge,  and  puddling  cinder  in  the  blast  furnace.  We 
may  expect  that  carbon,  and,  in  a  still  greater  degree,  silicon,  con- 


MANUFACTURE    OF   WROUGHT  IRON.  319 

tained  in  bar  iron,  will  reduce  the  protoxide  of  iron  in  the  cinder, 
and  leave  pure  silex,  or  other  matter ;  that  it  will,  at  any  rate,  de- 
stroy the  vitrified  texture  of  the  cinder  in  the  pores  of  the  iron.    A 
good  cinder,  of  general  application,  would  be  one  whose  vitreous 
nature  could  not  be  destroyed  by  the  influence  of  the  impurities  of 
the  iron.     A  gray,  glassy,  tough  blast  furnace  cinder  would  be  the 
best  of  all  materials  for  this  purpose  ;  but  it  may  be  impossible  to 
mix  such  matter  properly  with  iron,  or  to  mix  with  iron  any  glass 
which  contains  no  metallic  oxides,  and  which  is  not  acted  upon  by 
reducing  agents.     The  development  of  the  nature  of  cinder  will 
thus  be  the  surest  means  of  arriving  at  a  correct  understanding  of 
the  nature  of  bar  iron.     Carbon  will  reduce  protoxide  of  iron  from 
its  combination.     Therefore,  for  poor  metal,  the  latter  will  not  form 
a  satisfactory  cinder  until  all  the  carbon  of  the  metal  is  destroyed. 
Where  carbon  remains  in  wrought  iron,  re-heating  will  restore  the 
granular  texture  of  the  metal.    Any  metallic  oxide,  forming  glasses, 
which  can  be  reduced  to  metal  by  carbon,  is  useless  in  the  forma- 
tion of  forge  cinders,  for  it  would  not  serve  to  retain  the  vitrified 
character  of  the  enclosed  cinder.     Protoxide  of  manganese  is  bet- 
ter than  that  of  iron ;  it  is  only  slightly  affected  by  carbon  ;  but 
silicon  will  reduce  one  part,  and  combine  with  another  part  of  it. 
It  forms  an  excellent  glass,  which  resists  the  destructive  agency  of 
carbon.    Iron  manufactured  by  means  of  a  rich  manganese  cinder  is 
very  strong,  of  good  welding  properties,  and  retains  its  fibres  in  al- 
most any  heat,  and  even  when  suddenly  cooled  in  cold  water.     Be- 
sides manganese,  the  alkaline  earths  and  the  alkalies  proper  are  the 
only  substances  at  our  service.     Alkaline  earths  are  of  no  use  in  the 
forge,  for  the  temperature  of  the  hearth  is  low,  and  sufficient  time  is 
not  afforded  for  their  combination  with  silex;  they  serve  merely  to 
stiffen  the  cinder,  and  add  impurities  that  are  injurious  to  the  iron. 
When  present  in  large  quantity,  they  frequently  prevent  the  for- 
mation of  fibrous  iron.     The  alkalies  proper,  such  as  soda  and  pot- 
ash, ought  to  be  the  best  agents  in  forming  a  good  cinder  ;  still, 
experiments  have  not  confirmed  the  conclusions  which,  theoretically, 
have  been  arrived  at.     Until  the  present  time,  no  benefit  has  been 
derived  from  so  apparently  practicable  a  theory. 

Bad  pig  iron  contains  carbon,  silicon,  and  calcium,  which  should 
be  partially  removed ;  or,  if  not  removed — which,  in  some  instances, 
is  unnecessary — we  should  employ  a  cinder  which,  mixed  with  any 
metal,  is  not  affected  by  the  reviving  properties  of  the  impurities. 
If  we  melt  such  pig  iron,  and  add  to  it  carbonate  of  potash  or  of  soda, 


320  MANUFACTURE    OF   IRON. 

the  carbonate  will  not  combine  with  silex;  if  once  combined,  it  can- 
not effectually  remove  protoxide  of  iron  from  the  cinder;  it  serves 
the  purpose  of  simply  making  the  cinder  more  fusible ;  it  dissolves 
the  oxides  of  metals,  but  it  does  not  dissolve  silex,  lime,  and  mag- 
nesia; it  will  augment  the  fusibility  of  a  strong  alkaline  cinder,  and 
to  this  extent  promote  vitrification,  but  it  cannot  prevent  the  for- 
mation of  protoxide  of  iron.  Caustic  potash  or  caustic  soda  is  evapo- 
rated in  the  heat  of  a  puddling  furnace,  before  any  union  with  silex 
can  be  effected.  Potash  and  soda,  mixed,  are  of  greater  advantage, 
for  they  offer  a  stronger  resistance  to  the  action  of  the  heat ;  but 
our  own  experiments  have  convinced  us  that  even  these  are  inappli- 
cable, because  the  greater  part  of  the  alkalies  is  lost  in  evaporation. 
Were  it  practically  possible  to  make  a  cinder  composed  of  potash, 
soda,  and  silex,  and  mix  it  with  any  kind  of  metal,  however  bad  it 
may  be  in  our  estimation,  the  bar  iron  resulting  would  be  strong, 
its  fibres  durable,  and  it  could  be  welded  with  ease.  But  it  would 
lose  its  strength,  in  proportion  to  the  oxidation  of  its  foreign  matter, 
that  is,  the  matter  originally  combined  with  the  metal. 

From  these  statements,  we  infer  that  the  application  of  manganese 
is  the  best  means  of  improving  the  quality  of  wrought  iron.  To 
what  extent  this  improvement  may  be  applied,  has  been  already 
explained.  It  will,  we  hope,  be  more  clearly  understood  from  the 
following  considerations  deduced  from  experience : — 

k.  When  a  heat  is  drawn  and  shingled,  the  furnace  must  be  so 
uniformly  charged  as  to  prevent  the  re-melting  of  any  portion  before 
the  melting  of  the  rest.  This  is  accomplished  by  a  repeated  turning 
and  moving  of  the  iron.  The  melting  of  the  cinder  before  the  iron 
becomes  soft  is  a  disadvantage,  for  when  the  cinder  covers  the  frag- 
ments of  iron,  the  difficulties  of  breaking  the  iron  and  mixing  it 
with  the  cinder  are  augmented.  The  most  favorable  results  follow 
when  the  iron  and  cinder  melt  together,  that  is,  when  both  become 
pasty  at  the  same  time.  It  is  of  less  consequence  when  pig  iron  is 
the  more  fusible  than  when  the  reverse  is  the  case.  To  produce 
this  state  of  things  is  sometimes  a  difficult  matter ;  still,  upon  its  ac- 
complishment, success  mainly  depends.  This  difficulty  is  augment- 
ed by  the  fact  that  the  composition  of  the  cinder  is  not  a  matter  of 
indifference.  We  can  increase  or  diminish  the  fusibility  of  a  cinder 
by  adding  to  it  an  alkali,  or  silex ;  but  this  may  injuriously  affect 
the  iron  in  the  furnace.  White  metal  is  very  apt  to  make  a  strong 
alkaline  cinder,  rich  in  protoxide  of  iron  ;  this  cinder  will  not  melt 
sooner  than  the  iron  melts.  In  such  cinder,  poor  white  metal  works 


MANUFACTURE   OF  WROUGHT  IRON.  321 

too  fast ;  sufficient  time  is  not  afforded  for  the  metal  to  dissolve. 
Besides,  it  contains  too  large  an  amount  of  oxygen,  or  protoxide  of 
iron  ;  and  the  metal,  by  means  of  silicon  and  carbon,  is  converted 
into  an  infusible  white  iron.  In  such  cases,  a  cinder  which  contains 
just  so  much  silex  that  its  fusibility  will  be  increased  by  the  appli- 
cation of  an  alkali  is  preferable,  and  therefore  it  is  advisable  the 
lining  of  the  furnaces  should  be  of  fire  brick  or  stone.  Such  cinder 
will  increase  in  toughness,  at  first,  because  the  first  matter  liberated 
from  the  metal  is  silex;  and  the  addition  of  silex  to  a  silicious  cinder 
will  retard  its  fusibility,  and  afford  more  time  to  work  the  metal. 
In  this,  also,  we  perceive  the  utility  of  charging  the  iron  along  with 
the  cold  cinder.  Any  rich  cinder  will  afford  oxygen  to  the  melting 
metal,  but  the  application  of  it  in  too  large  amount  will  accelerate 
the  work  beyond  the  limits  of  prudence.  White  metal,  especially 
that  which  is  not  to  be  improved,  ought  to  be  melted-in  without  any 
cinder ;  but  the  grayer  the  metal  is,  the  longer  it  remains  fusible, 
and  the  greater  may  be  the  amount  of  cinder  which  can  be  charged 
along  with  the  cold  iron. 

Thus  far,  the  melting-in  of  the  iron  is  the  most  important  part  of 
the  operation  ;  but  it  is  evident  that  the  true  cause  of  the  difference 
in  work,  or  the  difference  in  cinder,  will  not  be  found  out  by  practical 
manipulation.  The  management  of  this  part  of  the  operation  is  the 
duty  of  the  manager  of  the  establishment ;  that  is,  the  manager 
should  give  the  general  directions,  in  accordance  with  which  the 
iron  should  be  worked.  If  we  are  in  doubt  as  to  the  propriety  of 
charging  cinder  along  with  the  metal,  it  is  better  to  forbear,  because 
we  are  more  sure  of  obtaining  good  work  by  melting  the  metal  in 
without  any  oxidizing  agent. 

When  the  iron  is  properly  melted  down,  that  is,  when  it  does  not 
rise,  or  exhibit  crystalized  particles,  we  may  accelerate  the  work  by 
throwing  in  good  iron  ore  finely  powdered,  roll-scales,  hammer-slag, 
chemical  compounds,  water,  or,  in  fact,  anything  which  experience 
has  shown  tends  to  consummate  the  desired  result.  The  matter 
thrown  into  the  furnace,  at  this  stage  of  the  operation,  will  deter- 
mine the  quality  of  the  iron  which  is  made.  If  we  desire  to  make 
hard  iron,  we  should  leave  a  certain  amount  of  silicon  and  carbon 
in  the  iron;  and  if,  at  the  same  time,  we  desire  to  produce  fibrous 
iron,  we  must  be  very  cautious  in  relation  to  applying  anything  of 
an  oxidizing  nature.  Neither  hammer-slag,  manganese,  water,  nor 
any  kind  of  iron  ore  is  applicable.  Active  manipulation,  and  a  fur- 
nace that  is  not  too  warm,  will  produce  a  hard,  strong,  fibrous  iron 
21 


322  MANUFACTURE   OF  IRON. 

of  a  dark  color,  but  not  adapted  for  blacksmith's  use.  By  the  in- 
troduction of  hammer-slag,  roll-scales,  or  magnetic  iron  ore,  a 
purer  iron  may  be  made.  Of  these,  magnetic  ore  is  the  preferable. 
Hammer-slag  and  cinder  always  contain  the  greater  part  of  the  im- 
purities of  the  iron  from  which  they  are  derived,  especially  sulphur 
and  phosphorus.  Cinder  is  the  very  element  which  removes  impu- 
rities ;  hence,  if  we  introduce  an  impure  material,  we  cannot  ex- 
pect a  pure  article  of  iron.  Cinder  has  only  a  limited  capacity  for 
sulphur  or  phosphorus ;  but  this  increases  proportionally  to  the 
amount  of  alkali  added  to  it.  Therefore,  even  though  we  introduce 
a  very  alkaline  cinder,  such  as  hammer-slag,  roll-scales,  and  forge 
cinder,  which  may  have  been  obtained  from  a  very  good  iron,  still, 
in  a  puddling  furnace,  its  capacity  for  impurities  is  diminished,  be- 
cause a  large  portion  of  the  alkali  is  absorbed  by  silex.  In  this  way, 
we  may  spoil  our  iron  in  the  furnace  with  the  very  material  we  employ 
for  its  improvement.  This  unfortunately  too  often  happens.  Mag- 
netic iron  ore  serves  all  the  purposes  of  hammer-slag;  and  if  it 
can  be  obtained  in  purity,  free  from  sulphurets,  it  is  by  far  the  safest 
of  all  means  for  improving  iron.  To  the  manufacturers  of  the  East, 
vast  quantities  of  magnetic  ore  from  Lake  Champlain,  or  New  Jer- 
sey, are  at  all  times  available.  The  Western  establishments  are 
less  advantageously  situated ;  for  the  only  serviceable  ore  which 
they  possess,  so  far  as  our  knowledge  extends,  is  the  compact  mag- 
netic ore  of  Missouri.  Still,  it  may  be  possible  to  obtain  useful  ores 
from  the  head  waters  of  the  Alleghany  River.  By  the  application  of 
good  ore,  and  by  the  observance  of  sound  principles  of  manipulation, 
we  may  obtain  iron  applicable  to  all  our  common  wants.  In  this 
way,  merchant  iron  of  the  finest  quality  may  be  made. 

If  it  is  our  intention  to  make  a  very  superior  iron,  neither  mag- 
netic ore  nor  hammer-slag  will  be  of  muck  service;  in  fact,  they 
are,  in  a  greater  or  less  degree,  injurious.  The  reason  of  this  is 
that,  in  a  very  alkaline  cinder,  the  solvent  power,  for  the  magnetic 
oxide,  is  rather  small ;  hence,  a  given  portion  of  the  flux  is  left  un- 
dissolved;  this,  as  an  isolated  matter,  will  be  visible  in  black  spots 
and  grains,  darkening  the  fracture,  and  adding  nothing  at  all  to  the 
strength  of  the  iron.  In  addition  to  this,  it  produces  coarse  pores, 
which,  for  fine  polished  work,  are  injurious.  A  fine,  superior  iron, 
of  great  cohesive  properties,  requires  a  very  alkaline,  well  fluxed, 
but  not  too  fusible  cinder — a  cinder  free  from  all  mechanical  ad- 
mixture, or  imperfectly  dissolved  matter.  An  alkaline  cinder  is  re- 
quired, to  remove  impurities  from  the  iron,  and  a  well  fluxed  cinder 


MANUFACTURE   OF  WROUGHT  IRON.  323 

to  form  fine  fibres.  A  strong,  tenacious  cinder  is  needed  to  resist 
the  union  of  the  iron  fibres,  as  well  as  the  deoxidizing  influence  of 
the  carbon  in  the  iron.  These  conditions  are  fulfilled  in  the  char- 
coal forge  only  with  the  best  kinds  of  metal ;  in  the  puddling  fur- 
nace only  where  the  lining  is  of  iron,  and  where  very  fusible  gray 
pig  is  employed.  Gray  pig  iron,  smelted  by  charcoal  in  small  amount, 
is  best  adapted  for  the  manufacture  of  a  superior,  very  strong,  pud- 
dled iron.  To  make  a  good  cinder,  we  require  strong  alkalies,  and 
if  even  in  excess,  the  cinder  must  be  perfectly  vitrified.  The  latter 
result  may  be  produced  by  applying  those  alkaline  salts  which  have 
the  pjpwer  of  dissolving  a  surplus  of  alkali,  or  metallic  oxides,  as,  for 
example,  protoxide  of  iron  ;  but  if  silex  is  to  be  removed,  the  acid 
of  the  introduced  salt  must  not  be  too  strong  to  resist  the  influence  of 
the  silex  upon  its  alkali.  Such  salts  are  the  carbonates,  borates, 
phosphates,  chlorides,  and  a  few  others  which  are  not  practicable 
in  our  manipulation.  Carbonates  of  the  alkaline  earths  require  the 
heat  and  time  which  a  blast  furnace  affords  to  be  of  any  service  ; 
and  the  carbonates  of  potash  and  soda  are  not  only  expensive,  but 
they  are  weak  solvents.  Borates  are,  of  all  fluxes,  the  most  perfect, 
but  of  a  carbonizing,  reducing  character;  therefore,  borax  is  a  most 
powerful  reducing  agent.  In  the  puddling  furnaces,  it  produces  a 
very  pure,  but  carbonized  iron.  Phosphates  may  be  considered  the 
most  perfect  of  fluxes,  in  puddling.  The  fear  which  prevents  some 
iron  manufacturers  from  placing  phosphorus  in  connection  with  iron, 
is  without  foundation  in  theory  or  practice.  Our  own  experience 
and  that  of  others  prove  that  there  is  not  the  least  difficulty  in  re- 
moving phosphorus  from  iron,  or  even  in  smelting  iron  ore  contain- 
ing phosphorus,  without  injury  to  the  metal,  that  is  to  say,  provided 
carbon  has  not  been  present  in  so  large  an  amount  as  to  leave 
phosphoric  acid  undecomposed.  Much  carbon  is  required  to  de- 
compose phosphoric  acid.  In  the  puddling  furnace,  phosphates 
cannot  be  decomposed,  and  they  remain  as  a  solvent  for  cinder  of  a 
very  alkaline  nature.  Any  free  alkali,  in  the  presence  of  carbon, 
will  abstract  phosphorus  from  iron ;  so,  also,  will  the  stronger 
alkalies,  such  as  barytas,  soda,  and  potash,  without  the  presence 
of  carbon.  Phosphates  are  soluble  in  any  silicate ;  and  if  silex 
increases,  so  that  no  alkali  is  left  with  which  the  phosphoric 
acid  can  combine,  the  latter,  unless  carbon  and  a  portion  of 
the  protoxide  of  iron  in  the  cinder  are  present  to  reduce  it,  will 
evaporate,  or  form  phosphuret  of  iron,  which,  of  course,  will  then 
remain  in  combination  with  the  iron.  Where  there  is  a  large 


324  MANUFACTURE    OF   IRON. 

amount  of  phosphorus  in  pig  iron,  we  require  an  equivalent  amount 
of  free  alkali  for  its  removal.  The  latter,  in  the  course  of  the 
puddling  process,  which  is  an  oxidizing  process,  will  become  a 
phosphate,  even  though  its  first  compound  was  a  phosphuret.  As 
a  phosphate,  it  cannot  be  of  injury  to  the  iron,  if  the  latter  is  free 
from  carbon  or  silicon.  Therefore,  the  wish  to  exclude  phosphorus 
containing  ores  is  an  unfounded  prejudice.  In  the  charcoal  forge, 
iron  containing  phosphorus  cannot  be  wrought  to  advantage.  As 
fluxes,  phosphates  occupy  a  position  between  borates  and  chlo- 
rides ;  they  are  not  so  much  of  a  reducing  agent  as  the  former,  nor 
so  much  of  an  oxidizing  agent  as  the  latter.  Chlorides,  sipch  as 
common  salt,  are  very  powerful  oxidizing  agents;  therefore,  in  the 
blast  furnace,  they  are  not  in  their  legitimate  place  ;  for,  to  make 
gray  iron,  when  a  considerable  amount  of  chlorine  or  a  chloride  is 
present,  is  impossible.  But  under  certain  conditions,  chlorides  are 
the  best  materials  to  improve  iron  in  the  refining  process  ;  they  are 
far  superior  to  the  strongest  alkalies.  They  are  more  permanent 
than  borates,  phosphates,  or  sulphates.  But,  in  the  presence  of 
carbon  in  excess,  they  are  very  volatile.  When  in  the  condition 
of  neutral  compounds,  they  are  but  little  inclined  to  associate  with 
other  salts;  if  the  latter  are  well  heated,  they  evaporate.  Chlorides 
possess  great  power  of  dissolving  alkalies  in  a  heated  condition ;  and 
before  chlorine  is  moved  by  silex,  it  will  drive  off  every  other  acid. 
The  employment  of  common  salt  in  the  refining  of  iron,  thus  shown 
to  be  unquestionably  useful,  is  of  very  limited  application,  owing  to 
the  difficulties  involved  in  its  use.  Where  carbon  is  present,  chlo- 
rides are  useless,  for,  in  a  given  heat,  they  will  evaporate  without 
leaving  a  trace  behind.  Where  the  heat  of  a  puddling  furnace  is 
quite  high,  as  in  the  melting  of  some  kinds  of  pig  iron  is  neces- 
sary, any  chloride  introduced  into  it  will  immediately  evaporate ; 
and  thus  time  is  not  afforded  for  its  combination  with  the  alkali  of 
a  cinder,  even  though  an  abundance  of  it  is  present.  We  now 
perceive  the  causes  of  the  divergence  between  science  and  practice. 
No  element  is  so  well  adapted  to  improve  iron  as  common  salt. 
But,  in  consequence  of  imperfect  knowledge,  its  application,  thus 
far,  has  been  extremely  limited.  In  fact,  because  it  has  failed  to 
produce  certain  results,  which  a  knowledge  of  its  nature  and  con- 
stitution ought  to  teach  us  we  have  no  reason  to  expect,  many  igno- 
rant persons  have  refused  to  employ  it  at  all.  In  puddling,  the  fur- 
nace ought  to  be  as  cold  as  possible,  if  salt,  or  any  chlorides,  are 
applied.  Therefore,  iron  which  melts  at  a  low  heat  is  preferable  ; 


MANUFACTURE    OF   WROUGHT   IRON.  325 

the  chlorides  must  be  very  dry,  and  finely  ground;  and  a  large  quan- 
tity of  cinder  is  required  to  prevent,  as  far  as  possible,  the  immediate 
contact  of  the  chlorides  and  iron,  before  the  solution  of  the  latter  takes 
place.  If  chlorides  are  brought  in  direct  contact  with  the  iron,  the 
chlorine  and  a  portion  of  the  iron  will  evaporate,  and  consequently, 
no  benefit  will  result  from  the  oxidizing  nature  of  the  cinder.  A 
cinder  containing  chlorine  is  a  powerful  oxidizing  agent.  Neither 
silex,  phosphorus,  sulphur,  manganese,  nor  iron  can  withstand  its 
influence,  even  though  it  exists  in  small  amount.  It  will  oxidize 
phosphorus,  sulphur,  and  carbon,  and  cause  their  destruction;  and 
of  these  elements  it  aids  to  form  acids,  which  are  either  combined  with 
the  alkali  of  the  cinder,  if  any  are  free,  or  are  ejected  in  the  form  of 
sulphurous  and  phosphorous  acids,  and  carbonic  oxide.  For  these 
reasons,  an  excess  of  salt  is  very  injurious,  for  it  will  evaporate,  and 
oxidize  a  large  portion  of  iron,  and  the  iron  which  is  produced  will 
be  dark  and  weak ;  but  by  applying  it  in  proper  quantity,  we  shall 
obtain  an  iron  which,  in  strength  and  color,  cannot  be  surpassed. 

The  above  are  the  only  elements  which  are  serviceable  for  the 
improvement  of  iron.  But,  as  this  statement  may  seem  to  require 
some  explanation,  we  shall  enter  upon  a  brief  consideration  of  those 
materials  which  might  possibly  be  made  to  serve  the  desired  pur- 
pose. We  shall  only  enumerate  oxidizing  agents,  for  these  alone  at 
present  interest  us. 

The  sulphates  are  almost  superior  to  chlorides  as  oxidizing 
agents ;  but  the  danger  of  decomposition,  by  which  sulphurets 
would  be  left  in  the  iron,  precludes  their  use.  The  decomposition 
of  the  acid  would  at  once  deprive  the  cinder  of  its  oxidizing  power, 
and  the  sulphuret  left  in  the  metal  will  remain  in  the  bar  iron, 
unless  the  cinder  contains  a  great  excess  of  alkali. 

Black  manganese  gives  off  its  oxygen  too  soon;  it  does  not  serve 
a  much  better  purpose  than  any  other  alkali.  It  possesses  greater 
strength  than  the  protoxide  of  iron,  but  it  is  inferior  to  soda  or  pot- 
ash. Iron  refined  under  its  influence  is  generally  hard,  fibrous, 
and  strong. 

Soda  and  potash  are  excellent  alkalies ;  but,  when  applied  in  such 
quantity  as  to  remove  sulphur  or  phosphorus,  they  are  too  fusible  to 
make  strong  iron.  In  small  quantities,  they  are  serviceable  where 
the  iron  is  of  good  quality ;  but  in  large  quantities,  they  increase  the 
fusibility  of  the  cinder  to  such  a  degree  that  the  iron  cannot  become 
strong  and  fibrous.  Besides,  so  strong  is  the  heat  of  a  puddling 


326  MANUFACTURE   OF  IRON. 

furnace,  that  the  greatest  part  even  of  the  carbonates  will  evaporate 
before  a  combination  of  the  alkali  and  the  cinder  is  effected. 

Oxide  of  lead  is  perfectly  useless,  because  of  the  shortness  of 
the  time  in  which  it  loses  its  oxygen,  but  we  have  applied  the  basic 
chloride  of  lead  with  success.  This  chloride  is  obtained  from  a 
mixture  of  litharge  and  common  salt,  in  the  proportion  of  four 
pounds  of  the  former  to  one  of  the  latter.  The  mixture  is  moistened 
with  water,  and  left  to  stand  for  twenty-four  hours.  We  were  in- 
duced to  make  this  experiment  from  having  observed  a  metal  which 
produced  the  most  beautiful  bar  iron  we  had  ever  seen.  The  metal 
was  white,  of  a  reddish  flesh-colored  cast;  it  was  smelted  from  an 
iron  ore  containing  lead  in  admixture.  The  lead  separated  from  the 
iron  in  the  lower  part  of  the  crucible.  This  metal,  white  as  any 
metal  can  possibly  be,  though  with  a  reddish  cast,  melted  as  thin 
as  any  gray  iron  containing  phosphorus.  It  kept  liquid  for  an 
unusual  length  of  time.  From  an  inferior  pig  iron,  we  obtained, 
by  the  application  of  the  chloride  of  lead,  an  excellent  quality  of 
iron,  though  not  equal  to  the  white  metal  smelted  from  the  lead 
containing  ores. 

To  the  following  material  we  wish  to  call  special  attention ;  not 
on  account  of  its  quality  as  a  flux,  but  because  of  the  facility  with 
which  it  can  be  applied.  Its  chemical  composition  is  remarkable; 
and  we  are  therefore  induced  to  reflect  upon  the  primary  condition 
of  those  materials  designed  for  the  improvement  of  iron  in  the  pud- 
dling furnace.  We  refer  to  the  magnetic  oxide  of  iron.  Expe- 
rience has  proved  that  hammer-slag,  roll-scales,  and  finely  powdered 
magnetic  oxide  are  the  best  means  of  promoting  the  process  of 
puddling.  They  do  not  produce  the  best  iron,  nor  the  fastest  work ; 
still,  it  is  unquestionable  that  they  are  the  most  available  materials 
at  our  service.  Black  magnetic  ore,  hammer-slag,  and  roll-scales 
constitute  the  magnetic  oxide  of  iron.  This  is  a  combination  of 
one  atom  of  protoxide  and  one  atom  of  peroxide  of  iron,  forming  a 
neutral  compound  which  is  less  easily  decomposed  than  the  peroxide, 
and  which  resists  the  influence  of  carbon  for  a  shorter  time  than  the 
protoxide.  If  such  a  compound  is  brought  in  contact  with  cinder, 
it  will  be  neutral,  because  it  melts  only  at  a  very  high  temperature ; 
and,  unless  carbon  or  some  other  reducing  agent  is  present,  it  will 
remain  in  the  cinder  in  its  original  integrity:  at  least,  it  will  resist 
decomposition  for  a  great  length  of  time.  At  first,  it  stiffens  the 
cinder.  This  is  just  what  is  required ;  for  a  strong  cinder  enables  us 
to  separate  the  iron  properly;  at  least,  this  is  the  object  which  we 


MANUFACTURE   OF   WROUGHT   IRON.  327 

always  aim  to  realize.  In  the  progress  of  the  work,  the  uncom- 
bined  particles  of  the  magnetic  oxide  will  come  in  contact  with  the 
melted  iron.  If  the  iron  is  of  good  quality,  and  carbon  alone  re- 
quires removal,  the  compound  oxide  will  be  decomposed  by  the 
carbon  ;  carbonic  oxide  will  escape  with  a  blue  flame  on  the  surface 
of  the  cinder  ;  and  the  protoxide  which  results  will  combine,  should 
it  come  in  contact  with  silex,  or  divide  the  silex  of  the  cinder  with 
the  other  alkalies.  With  respect  to  the  removal  of  carbon,  many  other 
materials  may  be  employed  with  even  greater  advantage;  but,  with 
regard  to  silex,  this  is  not  the  case.  Any  alkali  will  remove  silex 
from  the  iron ;  but  for  the  removal  of  silicon,  the  black  magnetic 
oxide  is  preferable  to  even  the  best  alkalies.  If  silicon  exists  in  the 
pig  iron — in  which  case,  oxygen  is  required  to  form  an  acid — and 
the  melted  iron  is  brought  in  contact  with  the  magnetic  oxide,  the 
peroxide  of  the  compound  is  decomposed;  oxygen  is  thus  imparted 
to  the  silicon  ;  the  newly-formed  silex  and  the  newly-formed  pro- 
toxide of  iron  will  then  combine  instantly.  According  to  the  laws 
of  chemistry,  this  is  the  most  favorable  condition  under  which  the 
combination  of  bodies  will  take  place.  In  this  case,  three  atoms  of 
magnetic  oxide  impart  oxygen  to  one  atom  of  silicon,  by  which 
means  a  single  silicate  is  formed.  A  more  perfect  compound  than 
the  sesquioxide  of  iron  can  scarcely  be  imagined;  still,  in  the  pro- 
gress of  knowledge,  some  more  advantageous  method  may  yet  be 
found  for  the  removal  of  silicon.  Sulphurets  and  phosphurets  are 
decomposed  with  facility  by  the  magnetic  oxide ;  but  the  resulting 
sulphates  and  phosphates  are,  in  turn,  decomposed  by  carbon ;  and 
as  no  wrought  iron  is  entirely  free  from  carbon,  the  magnetic  oxide 
is  not  the  best  material  at  our  service  for  the  removal  of  sulphur 
and  phosphorus. 

Great  attention  is  therefore  required  so  to  arrange  matters  in  the 
puddling  furnace  that  we  shall  have  a  cinder  slightly  less  fusible 
than  the  iron.  With  white  metal,  it  should  be  less  fusible  for  want 
of  alkali ;  and  with  gray  iron,  by  virtue  of  the  absence  of  silex  or 
acid.  But  in  most  cases,  it  is  advantageous  to  have  a  somewhat 
alkaline  cinder,  because  a  better  yield  is  produced.  After  the  iron 
is  melted,  and  fluxes  are  applied,  the  cinder  begins  to  thicken,  long 
blue  flames  escape  at  the  surface,  and  the  whole  mass  begins  to  fer- 
ment. Blue  flames  appear  only  when  the  work  goes  on  well ;  in 
which  case  carbonic  oxide  is  formed  below  the  cinder.  If  the  cin- 
der is  too  alkaline,  that  is,  if  it  contains  too  much  iron,  no  such 
flames  appear;  but  a  lively  ebullition  is  visible  on  the  surface  of  the 


328  MANUFACTURE   OF  IRON. 

cinder.  The  same  result  occurs,  if  we  throw  in  oxygen  in  too  large 
amount,  or  that  which  is  too  loosely  fixed.  The  reason  of  this  is 
the  formation  of  carbonic  acid,  instead  of  carbonic  oxide,  below  the 
cinder ;  and  it  requires  very  good  metal  indeed  to  make  valuable 
iron  by  such  manipulation.  To  produce  blue  flames,  and  to  pre- 
vent the  formation  of  carbonic  acid,  the  most  effective  means  we 
possess  are  a  cold  hearth  at  the  commencement  of  the  operation, 
diligent  manipulation,  and  the  application  of  the  smallest  quantity 
of  fluxes  that  is  commensurate  with  success. 

After  the  iron  has  risen,  and  the  mass  has  begun  to  ferment,  the 
quality  of  the  iron  is  fixed.  Nothing  but  industry  is  now  required, 
to  obtain  as  large  a  yield  as  possible,  and  to  make  the  iron  work 
well  at  the  squeezer.  To  an  unphilosophical  mind,  the  fermenta- 
tion of  the  metal  appears  to  be  a  singular  phenomenon.  In  fact, 
few  sights  are  more  beautiful  than  that  of  a  mass  of  iron  from  700 
to  1000  pounds'  weight,  occupying  at  first  scarcely  the  depth  of  an 
inch  in  the  hearth  of  the  furnace,  gradually  rising,  fermenting,  and 
boiling,  while  small  particles  of  iron,  in  apparently  spontaneous 
motion,  suddenly  appear  on  the  surface  in  small  clusters  like  brilliant 
stars,  and  then  as  suddenly  disappear.  This  fermentation  happens 
only  with  metal  that  contains  a  given  amount  of  carbon.  White 
metal,  which  contains  little  or  no  carbon,  does  not  ferment.  Not 
only  the  amount  of  carbon,  but  the  composition  of  the  cinder,  in- 
fluences fermentation.  The  cause  of  the  boiling  is  nothing  else 
than  the  evolution  of  gas,  generated  by  the  combination  of  oxygen 
and  carbon.  If  the  cinder  which  covers  the  liquid  iron  is  very 
fusible,  the  gas  escapes  in  bubbles  on  its  surface,  and  the  metal 
does  not  rise.  If  the  cinder  possess  a  certain  tenacity,  if  it  is  slimy 
like  soap  water,  it  will  resist  the  escape  of  the  gas,  and  rise  until 
its  surface  isc  lose  to  the  flame  of  the  furnace,  when,  becoming 
warmer,  and  more  liquid,  its  power  of  resistance  is  diminished. 
The  slimy  consistency  of  the  cinder  is  produced  by  silex,  but  more 
perfectly  by  clay ;  the  latter  may  be  derived  from  the  pig  iron,  or 
it  can  be  charged  with  the  fluxes.  If  we  reflect  upon  this  quality 
of  clay,  which  is  the  same  under  all  circumstances,  we  shall 
arrive  at  the  cause  of  its  beneficial  influence  upon  iron.  Our  exer- 
tions are  chiefly  directed  towards  obtaining  a  well-defined  cinder ; 
neither  too  acid  nor  too  alkaline.  Clay  fulfils  these  conditions.  It 
serves  both  as  an  acid  and  as  an  alkali.  It  fluxes,  and  in  the  mean 
time,  will  strengthen  the  body  of  the  cinder.  It  is  very  serviceable 
in  removing  phosphorus,  for  with  phosphoric  acid  it  forms  a  fusible 


MANUFACTURE   OF   WROUGHT   IRON.  329 

compound  of  great  solvent  power.  Though  experience  were  not  in 
its  favor,  a  consideration  of  its  quality  ought  to  convince  us  of  its 
great  utility  in  the  puddling  furnace.  If  the  above  explanation  of 
the  causes  of  fermentation  is  correct,  it  follows  that  the  process  de- 
pends upon  the  quality  of  the  metal,  and  upon  the  nature  of  the 
cinder.  Nevertheless,  an  experienced  and  skillful  workman  will 
make  almost  any  metal  boil,  provided  it  contains  but  little  carbon. 

As  the  fermentation  proceeds,  the  iron  coagulates,  that  is,  crystal- 
izes  below  the  cinder.  As  the  small  particles  formed  still  contain 
a  portion  of  carbon,  which  combines  with  oxygen  derived  from  the 
cinder,  the  newly-formed  carbonic  oxide  rises,  and,  in  its  ascent, 
draws  along  with  it  a  small  crystal  of  iron,  which,  coming  to  the 
surface,  burns  for  a  moment  with  a  vivid  light,  and  then  disappears, 
because,  after  it  loses  its  bubble  of  gas,  there  is  nothing  to  coun- 
teract its  gravity.  This  motion  of  the  particles  of  the  iron  continues 
until  the  carbon  of  the  metal  is  exhausted,  or  until  the  oxygen  of  the 
cinder  is  so  diminished  that  no  more  gas  can  be  formed ;  after  which 
the  cinder  gradually  contracts,  and  sinks  to  the  bottom  of  the  fur- 
nace, leaving  the  iron,  to  a  greater  or  less  degree,  unprotected,  and 
exposed  to  the  heat.  Metal  containing  silex,  silicon,  phosphorus, 
sulphur,  but  no  carbon,  will  not  ferment,  for  no  gas  is  liberated  to 
cause  fermentation.  Therefore,  such  metal  is  greatly  exposed  to 
the  heat  and  oxygen  of  the  furnace,  and  works  too  quickly;  hence 
the  difficulty  of  improving  it,  even  though  it  is  very  fusible.  We 
thus  see  the  advantage  of  fermentation  in  working  inferior  pig  iron. 
As  boiled  iron  is  preferable  for  small  iron  rods,  wire  iron,  black- 
smiths' iron,  and  nails,  we  should  always  seek  to  obtain  gray  pig 
for  the  boiling  process. 

After  the  fermentation  is  finished,  the  oxidation  of  the  iron  com- 
mences; for,  if  the  process  has  been  properly  conducted,  all  the 
previous  operations  will  have  tended  only  to  remove  impurities. 
The  time  at  which  this  takes  place  depends  upon  the  time  occupied 
in  finishing  the  heat,  and  upon  the  amount  of  silex  the  cinder  con- 
tains. The  oxidation  of  the  iron  serves  to  flux  the  slag,  which  be- 
comes more  and  more  liquid,  as  the  temperature  of  the  hearth 
increases.  At  this  stage  of  the  process,  the  utility  of  the  iron 
boshes  is  evident,  for,  should  the  furnace  have  been  lined  with 
bricks  or  stones,  all  the  alkalies  we  have  applied,  and  all  the  iron 
which  has  been  burnt,  would  have  been  wasted  in  their  destruc- 
tion. Besides,  the  main  object  of  our  skill  and  industry  is  to  in- 


330  MANUFACTURE   OF  IRON. 

crease  the  amount  of  alkali  in  the  cinder;  but  this  object  is  directly 
counteracted  by  brick  and  stone  boshes. 

I.  Having  delineated,  though  by  no  means  having  exhausted,  the 
various  matters  which  relate  to  puddling,  we  shall  take  a  critical 
view  of  the  present  mode  of  refining.  We  shall  also  investigate 
the  cause  of  the  improvement  which  results  from  the  sudden  cool- 
ing of  metal,  and  shall  conclude  the  chapter  by  a  few  general  re- 
marks on  wrought  iron. 

The  run-out  fire,  which  is  generally  employed  for  refining  iron, 
is  based  upon  principles  derived  from  the  charcoal  forge.  Before  hot 
blast  was  introduced  into  blast  furnace  operations,  this  was  doubt- 
less a  useful  apparatus.  Pig  metal  which,  fifteen  years  ago,  would 
have  been  considered  worthless  for  the  forge,  is  now  employed  in 
the  manufacture  of  iron.  The  run-out  fire  labors  under  the  same 
difficulties  which  exist  in  relation  to  the  puddling  furnace  with  iron 
boshes.  For  iron  which  contains  carbon  in  small  amount,  or  in 
chemical  combination,  its  hearth  is  too  cold.  From  gray  charcoal 
pig  iron,  of  good  quality,  the  run-out  produces  a  tolerably  useful 
article.  But  we  do  not  need  it  for  this  purpose.  Cold  blast  gray 
pig  may  be  worked  to  advantage  in  the  puddling  furnace  with- 
out Difficulty.  Since  the  introduction  of  hot  blast — that  is,  since  the 
use  of  anthracite  and  stone  coal — quite  a  revolution  has  taken  place 
in  the  chemical  constitution  of  pig  iron :  the  amount  of  chemi- 
cally combined  carbon  has  increased;  silicon  and  other  reduced 
matter  are  more  generally  present ;  and  even  the  grayest  specimens 
of  metal  are  not  free  from  unoxidized  elements.  To  these  causes,  the 
difficulty  of  refining  hot  blast  iron  may  be  mainly  attributed.  Our 
previous  investigations  have  proved  that  a  high  heat  is  required  for 
the  removal  of  silicon:  but  a  still  more  necessary  element  is  a  cin- 
der which  does  not  too  freely  yield  its  oxygen.  To  what  extent 
does  the  run-out  fire  fulfil  these  conditions  ?  With  respect  to  heat, 
it  is  but  little  better  than  the  puddling  furnace ;  and  with  respect  to 
cinder,  it  answers  scarcely  a  better  purpose.  Analysis  has  shown 
that  the  cinder  of  the  run-out  fire  contains  as  much  protoxide  of 
iron  as  the  cinder  of  a  puddling  furnace.  A  finery  cinder  from 
Dudley,  England,  contained  silex  27.6,  protoxide  of  iron  61.2,  alu- 
mina 0.4,  and  phosphoric  acid.  If  we  melt  very  impure  pig  iron  in 
such  a  cinder,  we  cannot  produce  iron  of  good  quality;  this  is  espe- 
cially the  case  should  the  iron  have  been  smelted  by  hot  blast.  For 
the  melting  of  such  iron,  we  require  a  cinder  containing  less  alkali. 
Less  alkali  is  required  to  make  good  iron  in  puddling.  From  the 


MANUFACTURE   OF   WROUGHT  IRON.  331 

amount  of  iron  in  this  cinder,  it  is  evident  that  the  run-out  fire  can- 
not improve  bad  pig  iron  in  any  high  degree,  unless  there  is  a  serious 
loss  in  metal.  That  this  loss  occurs  is  shown  not  only  from  con- 
clusions theoretically  arrived  at,  but  from  observation.  Whatever 
advantage  the  run-out  fire,  in  this  case,  possesses,  is  that  of  a 
division  of  labor,  which,  of  course,  we  are  not  disposed  to  rate 
very  highly. 

We  believe  that,  in  the  construction  of  the  run-out  fire,  but  little 
science  and  philosophy  have  been  embodied.  At  all  events,  but 
one  principle  governs  the  present  case;  that  is,  bringing  the  inferior 
qualities  of  metal,  in  the  cheapest  possible  way,  to  a  higher  standard. 
The  idea  of  making  white  metal  was  undoubtedly  derived  from  the 
ancient  method  by  which  such  metal  was  made  in  the  blast  furnace. 
The  latter  metal,  when  smelted  from  good  ore,  was,  and  still  is,  a 
prime  article  in  the  charcoal  forge.  Since  the  introduction  of  coke, 
anthracite,  poor  ores,  and  hot  blast,  the  iron  business  has  undergone 
a  change.  At  the  present  time,  we  cannot  avoid  producing  pig 
iron  which,  a  few  years  ago,  would  have  been  considered  worthless. 
This  metal  it  is  now  our  object  to  bring  to  as  high  a  standard  as  the 
best  iron  of  the  ancients.  In  the  accomplishment  of  this  object,  it 
is  evident  that  cautious  manipulation  and  scientific  knowledge  are 
required.  We  cannot  believe  that  any  one  doubts  that  the  quality 
of  our  worst  pig  iron  is  equal  to  that  of  the  ores  from  which  steel 
metal  is  made.  If  such  is  the  case,  it  should  not  be  deemed  an 
impossibility  to  make  steel  metal  from  our  most  inferior  pig  iron. 

There  would  be  no  necessity  for  making  white  metal  were  it  not 
for  the  railroad,  boiler-plate,  and  heavy  bar  iron  which  is  needed. 
For  these  purposes,  boiled  does  not  answer  so  well  as  puddled  iron. 
But,  if  such  iron  is  necessary,  it  should  be  well  made.  The  run- 
out fire  is  imperfectly  adapted  to  accomplish  this  result.  By  destroy- 
ing the  carbon  in  pig  iron,  without  removing  its  impurities,  it  fails 
to  produce  a  metal  fit  for  boiling.  Therefore,  the  run-out  fire  de- 
stroys the  element  necessary  to  make  metal  boil,  without  producing 
a  metal  profitable  for  puddling.  Hot  blast  iron  would  be  an  excel- 
lent metal  for  boiling,  were  it  possible  to  remove  its  impurities 
without  destroying  its  carbon.  Still,  it  is  not  impossible  to  remove 
impurities  and  carbon  together,  and  thus  make  a  useful  metal  for 
puddling. 

The  finery  is  considered  a  link  between  the  blast  furnace  and  the 
puddling  furnace ;  that  is,  it  is  believed  to  occupy  the  same  rela- 
tive position  between  these  furnaces  that  the  blast  furnace  occupies 


332  MANUFACTURE    OF  IRON. 

between  the  ore  and  the  finery.  The  blast  furnace  is  an  apparatus 
designed  for  the  removal  of  impurities  with  the  least  possible  loss  of 
iron.  It  answers  the  purpose  of  its  construction  excellently.  But 
what  is  the  fact  with  respect  to  the  finery?  Simply  this:  the  cinder 
from  the  finery  contains  more  iron  than  that  from  the  puddling  fur- 
nace; and,  when  we  consider  that  the  contact  of  coke  or  anthracite 
increases  the  amount  of  silex  in  the  former,  we  find  that  there  is  a 
far  greater  loss  of  metal  in  the  run-out  fire  than  would  result  from 
the  same  pig  iron  in  the  puddling  furnace.  If  this  is  the  only  ad- 
vantage derivable  from  the  finery,  it  is  surely  far  preferable  to 
take  the  worst  kind  of  pig  iron  directly  to  the  puddling  furnace. 

We  trust  that  some  practical  men  will  be  sufficiently  interested 
in  this  subject  to  endeavor  to  construct  something  better  adapted 
to  our  wants  than  this  exceedingly  imperfect  apparatus.  If  heat, 
and  a  cinder  to  protect  the  iron  can  be  obtained,  all  the  conditions 
of  a  good  finery  will  be  fulfilled. 

m.  The  philosophy  of  the  improvement  of  metal  consists  in  the 
circumstance  that  a  part  of  its  impurities,  which  are  originally  in 
chemical  combination,  are  converted  into  mechanical  admixtures. 
Iron  containing  a  small  amount  of  carbon,  silicon,  or  phosphorus, 
is  always  more  hard  and  strong  than  pure  iron.  Pure  iron  is  quite 
soft.  Impure  iron  has  the  property  of  crystalizing  on  being  sud- 
denly cooled.  The  size  of  these  crystals  is  proportional  to  the  amount 
of  carbon  in  chemical  combination  the  iron  contains,  in  proportion 
to  other  matter.  Between  the  crystals,  minute  spaces  are  left,  which 
serve  for  the  absorption  of  oxygen.  By  this  means,  silicon  and 
calcium  may  be  oxidized;  but  such  is  not  the  case  with  carbon, 
phosphorus,  and  sulphur.  Therefore,  the  metal  improves  in  quality 
in  proportion  as  oxygen  finds  access  to  its  impurities.  For  this 
reason,  the  habit  of  running  metal,  or  any  kind  of  pig  iron  designed 
for  the  forge,  into  iron  chills,  is  a  good  one,  and  is  worthy  of  imita- 
tion wherever  it  is  applicable.  By  this  means,  the  absence  of 
sand  and  the  cleanliness  of  the  metal  are  secured.  For  the  same 
reason,  the  metal  is  tempered;  that  is,  the  plates  of  metal,  or,  as  in 
some  parts  of  Austria,  rosettes  of  metal,  are  piled  up  with  small 
charcoal,  braise,  and  exposed  to  a  lower  temperature  than  a  cherry- 
red  heat,  for  twenty-four  or  forty-eight  hours,  in  a  kind  of  large 
bake  oven.  By  this  method,  the  value  of  the  metal  is  improved 
for  the  manufacture  of  soft  and  fibrous  iron.  It  is  not  applicable 
to  plates  from  which  steel  is  to  be  made. 

n.  Wrought  iron,  if  of  good  quality,  is  silvery  white,  and  fibrous ; 


MANUFACTURE  OF   WROUGHT  IRON.  333 

carbon  imparts  to  it  a  bluish,  and  often  a  gray  color  ;  sulphur  a 
dark  dead  color,  without  a  tinge  of  blue  ;  silicon,  phosphorus,  and 
carbon  a  bright  color,  which  is  the  more  beautiful  the  more  the  first 
two  elements  preponderate.     The  lustre  of  iron  does  not  depend 
principally  upon  its  color ;  for  pure  iron,  though  silvery  white,  re- 
flects little  light.     A  small  quantity  of  carbon  in  chemical  combi- 
nation, phosphorus,  or  silicon  increases  the  brilliancy  of  its  lustre. 
Its  lustre  is  diminished  by  silex,  carbon  in  mechanical  admixture, 
cinder,  lime,  sulphur,  or  magnesia.  Good  iron  should  appear  fresh, 
somewhat  reflex  in  its  fibres,  and  silky.     A  dead  color  indicates  a 
weak  iron,  even  though  it  is  perfectly  white.     Dark,  but  very  lus- 
trous iron  is  always  superior  to  that  which  has  a  bright  color  and 
feeble  lustre.     Coarse  fibres  indicate  a  strong,  but,  if  the  iron  is 
dark,  an  inferior  article,  unfit  for  the  merchant  or  the  blacksmith. 
But,  where  the  iron  is  of  a  white,  bright  color,  they  indicate  an  ar- 
ticle of  superior  quality  for  sheet  iron  and  boiler-plate,  though  too 
soft  for  railroad  iron.     For  the  latter  purpose,  a  coarse,  fibrous, 
slightly  bluish  iron  is  required.     Iron  of  short  fibre  is  too  pure ;  it 
is  generally  hot-short,  and,  when  cold,  not  strong.     This  kind  of 
iron  is  apt  to  result  from  the  application  of  an  excess  of  lime.   Its 
weakness  is  the  result  of  the  absence  of  all  impurities.     The  best 
qualities  of  bar  iron  always  contain  a  small  amount  of  impurities. 
Steel  ceases  to  be  hard  and  strong  if  we  deprive  it  of  the  small 
amount  of  silicon  it  contains,  or  if,  by  repeated  heating,  that  sili- 
con is  oxidized.     This  is  the  case  with  bar  iron.     If  we  deprive 
it  of  all  foreign  admixtures,  it  ceases  to  be  a  strong,  tenacious,  and 
beautiful  iron,  and  becomes  a  pale,  soft  metal,  of  feeble  strength 
and  lustre.    Good  bar  or  wrought  iron  is  always  fibrous  ;  it  loses  its 
fibres  neither  by  heat  nor  cold.     Time  may  change  its  aggregate 
form,    but  its  fibrous  quality   should  always  be    considered   the 
guarantee  of  its  strength.     Iron  of  good  quality  will  bear  cold 
hammering  to  any  extent.    A  bar  an  inch  square,  which  cannot  be 
hammered  down  to  a  quarter  of  an  inch  on  a  cold  anvil  without 
showing  any  traces  of  splitting,  is  an  inferior  iron. 


334  MANUFACTURE    OF   IRON. 


CHAPTER   V. 

FORGING  AND  ROLLING. 

THE  machines  adapted  for  forging  and  condensing  wrought  iron 
vary  both  in  principle  and  in  form.  This  department  of  the  labors 
of  the  iron  master  is  very  extensive.  But,  as  our  treatise 
must  necessarily  be  restricted  within  certain  limits,  and  as  this 
branch  of  iron  manufacture  is  already  highly  cultivated  in  this 
country — our  establishments  excelling  in  finish  those  of  Europe 
generally,  and  in  some  respects  particularly — we  shall  devote  the 
present  chapter  to  a  mere  enumeration  of  the  machines  required  in 
an  iron  factory,  and  explain  the  principles  upon  which  each  is  con- 
structed. We  are  satisfied  that,  if  a  higher  degree  of  perfection  is 
needed  in  this  department,  it  will  be  realized  by  the  intellect,  skill, 
and  industry  of  our  practical  engineers. 

I.  Forge  Hammers. 

a.  The  most  simple  machine  by  which  iron  is  forged  is  the  Ger- 
man forge-hammer,  often  called  the  tilt-hammer.  This  machine, 
often  of  a  fanciful  form,  is  very  extensively  employed.  The  lead- 
ing principle  which  we  seek  to  secure  in  its  construction  is  solidity; 
and  every  variety  of  form  has  been  invented  simply  to  give  per- 
manency to  the  structure,  which  is  mainly  endangered  by  the  action 
and  reaction  of  the  strokes.  The  common  form  of  a  forge-hammer 
with  a  wooden  frame  is  represented  by  Fig.  95.  a  The  cast  iron 
hammer,  which  varies  in  weight,  according  to  the  purposes  for 
which  it  is  designed,  from  50  to  400  pounds.  For  drawing  small 
iron  and  nail  rods,  a  hammer  of  the  former  size  is  sufficiently 
heavy  ;  but  for  forging  blooms  of  from  60  to  100  pounds  in  weight, 
a  hammer  weighing  300  or  400  pounds  is  employed.  Such  a  ham- 
mer is  represented  by  Fig.  96,  in  detail.  It  should  be  cast  from  the 
strongest  gray  iron,  and  secured  by  wooden  wedges  to  the  helve  b. 
The  fastening  of  the  hammer  to  its  helve  is,  in  many  cases,  effected 


FORGING  AND  ROLLING. 


335 


with  difficulty,  especially  if  tlie  cast  is  weak  ;  and  to  this  weakness 
attention  must  be  paid.     If  the  hammer  is  of  good  cast  iron,  or,  as 


Fig.  95. 


Tilt-hammer. 


in  many  instances,  of  wrought  iron,  there  is  no  difficulty  in  wedgi.   , 
it.     If  wooden  wedges  are  properly  applied,  and  well  tightened . 


Fit 


Hammer. 


long  iron  wedges  may  be  driven  in  between  them  ;  but  these  must 
be  so  placed  as  not  to  injure  the  helve,  or  lie  too  close  to  the  iron 


336  MANUFACTURE   OF   IRON. 

of  the  hammer.  These  iron  wedges  are  then  secured  by  a  sledge, 
weighing  thirty  or  forty  pounds,  with  a  long  handle.  This  is  sus- 
pended on  a  rope,  or,  what  is  better,  a  small  iron  rod  or  chain,  ad- 
justed upon  the  head  of  the  wedge,  by  which  means  a  horizontal 
stroke  is  secured.  The  face  of  the  hammer  is  polished,  and  in  case 
long  bar  iron  is  to  be  drawn,  it  is  frequently  twisted  with  the  helve. 
c  The  anvil,  a  cast  iron  block,  about  the  weight  of  the  hammer ; 
but  it  may  be  of  less  weight  if  the  iron  stock  d  is  employed,  e  A 
log  of  wood  from  six  to  eight  feet  in  length,  and  frequently  four 
feet  in  diameter.  This  log  is  secured  at  its  base  and  top  by  iron 
hoops.  It  rests  upon  timber  laid  across  piles  very  stoutly  driven  in 
the  ground.  Such  a  foundation  for  the  log,  or  hammer-stock,  is  re- 
quisite, because  rock,  or  the  most  solid  ground,  forms  at  best  but  an 
insufficient  base.  The  two  standards — sometimes  of  wood,  some- 
times of  iron — in  which  the  hammer  has  its  fulcrum,  need  no  de- 
scription; neither  does  the  mode  of  fastening  them.  All  that  is 
required  here  is  strength,  no  amount  of  which  is  superfluous.  The 
helve  b  is  of  sound,  dry  hickory,  or,  more  commonly,  of  white  oak. 
The  fulcrum  #,  a  cast  iron  ring,  is  represented  by  Fig.  97 ;  this 

Fig.  97. 


Helve-ring. 

must  be  tightly  wedged  upon  the  helve,  i  A  wrought  iron  ring, 
fastened  to  the  helve  ;  on  its  upper  side,  it  receives  the  taps  of  the 
cams  ;  on  the  lower  side,  it  strikes  against  a  vibrating  piece  of  tim- 
ber for  the  purpose  of  increasing,  by  recoil,  the  force  of  the  ham- 
mer. It  is  easily  understood  that,  if  the  hammer  is  thrown  up  with 
force,  the  reaction  upon  the  fulcrum  and  framework  must  be  im- 
mense. This  is  especially  the  case  where  a  high  stroke  of  the  ham- 
mer is  required,  as  in  forging  blooms.  The  destructive  power  of 
this  reaction  increases  with  the  ratio  of  the  weight,  and  according 
to  the  square  of  the  speed.  That  is  to  say,  if  the  hammer  strikes 
with  100  pounds  force  against  A,  when  seventy  strokes  per  minute 
are  made,  it  will,  when  140  strokes  per  minute  are  made,  strike 


FORGING  AND  ROLLING.  337 

•with  a  force  of  400  pounds.  The  same  rule  is  applicable  in  rela- 
tion to  the  space  described  by  the  hammer.  If  the  hammer,  lifted 
ten  inches,  strikes  with  a  force  of  1000  pounds,  it  will,  when  lifted 
twenty  inches,  strike  with  a  force  of  4000  pounds.  This  shows 
the  great  increase  of  power  which  follows  that  of  speed,  and  imparts 
some  idea  of  the  reaction  which  machinery  of  this  kind  sustains. 
If  the  length  of  the  shorter  part  of  the  helve,  from  i  to  </,  is  very 
small  proportionately  to  that  of  the  longer  part,  the  reaction  of  course 
increases,  in  a  high  degree,  upon  the  vibrating  beam.  This  latter 
circumstance,  and  the  reaction  upon  the  fulcrum,  made  it  necessary 
that  the  recoil  should  be  brought  more  upon  the  hammer  itself.  In 
the  attempt  to  effect  this  result,  a  great  variety  of  forms  of  the  ham- 
mer was  produced.  The  shaft  Jc  is  commonly  made  of  wood.  If 
the  motive  power  is  water,  the  waterwheel  is  directly  fastened  upon 
it ;  if  it  is  steam,  a  flywheel  is  attached,  and  the  power  applied  by 
leather  straps  or  belts.  The  cast  iron  wheel  m,  which  is  often  of 
an  octagonal  form,  but  generally  round,  must  be  strong  ;  in  it  the 
cams  I  are  fastened. 

These  hammers  are  troublesome  implements.  For  shingling 
blooms,  they  can  be  replaced  by  squeezers;  but  they  are  required 
for  drawing  bar  iron,  and  making  pattern  iron,  such  as  sledge 
moulds.  An  ingenious  inventor  has  a  fair  field  for  improving  the 
present  machinery.  The  steam  hammer  of  Messrs.  Merrick  and 
Towne,  Philadelphia,  is  a  fine  implement,  and  is  well  adapted  for 
forging  steam-engine  shafts :  but  the  smaller  kind  of  these  steam 
hammers  work  so  slowly  that  they  do  not  answer  for  drawing  iron ; 
at  least,  they  make  but  eighty  or  100  strokes  per  minute ;  while  it 
is  necessary  that  a  hammer  suitable  for  drawing  iron  should  make 
at  least  150  strokes,  and  smaller  hammers  from  150  to  300,  and 
even  400  strokes  per  minute.  The  hammer  should  be  an  independ- 
ent machine,  with  an  independent  power.  It  cannot  be  connected 
with  other  machinery,  for  the  speed  of  the  hammer  should  be  per- 
fectly under  the  control  of  the  hammerman,  who  should  be  enabled 
to  make  twenty,  or  400  strokes,  at  pleasure.  Steam  is  the  cheapest 
motive  power  in  iron  works,  because  surplus  heat  for  its  genera- 
tion is  always  available. 

b.  For  the  shingling  of  blooms,  and  slabs  for  boiler-plate  and 
sheet  iron,  the  iron  T  hammer  is  generally  employed.  Fig.  98  re- 
presents a  side  view,  and  in  some  parts  a  section  of  the  hammer, 
flywheel  shaft,  and  the  stock  of  the  anvil.  The  whole  machinery 
is  constructed  of  cast  iron,  with  the  exception  of  the  foundation 
22 


338 


MANUFACTURE   OF   IRON. 


below  ground,  which  is  built  of  timber.     The  weight  of  the  whole 
amounts  to  more  than  from  thirty  to  forty  tons.     The  hammer  a 


Fig.  98. 


Large  forge  hammer — T  hammer. 

generally  weighs  from  four  to  five,  the  anvil  stock  b  from  five  to 
eight,  and  the  cam  ring  c  from  three  to  four,  tons.  This  machine  is 
now  superseded  by  better  machinery  ;  and  as  no  one,  at  present, 
thinks  of  erecting  a  new  T  hammer,  a  full  description  of  it  is  un- 
necessary. 

c.  A  hammer  designed  for  the  same  purpose  as  the  above  T  ham- 
mer, and  quite  as  heavily  and  clumsily  constructed,  is  used  in  some 
parts  of  Europe,  though  not,  to  our  knowledge,  in  the  United 
States.     In  this  machine,  the  power  is  applied  between  the  anvil 
and  the  standards. 

d.  As  many  T  hammers  are  yet  in  use,  and  will  doubtless  remain 
in  use  for  the  shingling  of  slabs,  it  will  probably  be  of  advantage  to 
mention  an  ingenious  jack.     With  the  common  jack,  the  catching 
is  difficult,  if  the  resting-place  is  worn  out,  or  if  an  inexperienced 
workman  takes  hold  of  it;  so  much  so,  indeed,  that  the  life  and 
limbs  of  those  around  the  hammer  are  in  danger.     In  the  illustra- 
tion, a  lever  /,  made  of  wrought  iron,  is  represented ;  this  turns 


FORGING  AND  ROLLING.  339 

round  a  pin  placed  near  it,  and  rests  on  the  anvil  stock,  g  is  a 
handle  to  a  small  iron  rod,  fastened  to  the  lever/.  By  moving  this 
lever,  a  small  boy  sitting  at  g,  and  protected  from  the  sparks  by  a 
board,  has  it  in  his  power  to  arrest  the  hammer  at  any  moment 
without  difficulty.  This  simple  machine  is  infallible,  and  deserves 
to  be  employed.  Besides,  it  is  cheaper  than  the  old  jack. 

e.  The  steam  hammer,  before  mentioned,  is  a  highly  useful  ma- 
chine for  shingling  blooms  or  slabs,  in  an  establishment  where  a 
heavy  hammer  is  necessary.  It  is  somewhat  complicated,  and  the 
perfect  manner  in  which  its  valves  move  cannot  be  intelligibly  ex- 
hibited by  a  woodcut.  Fig.  99  is  a  representation  of  the  general 
form  of  the  entire  machine. 

Fig.  99. 


Steam  hammer. 

/.  The  shingling  of  blooms  from  balls  is  generally  performed  by 
welding  a  rod  of  about  an  inch  square,  previously  heated,  to  the 
ball.  This  rod  serves  as  a  handle  to  move  the  bloom  under  the 
hammer,  and,  when  the  bloom  passes  to  the  rollers,  as  is  the  case 
in  puddling  forges,  or  when  it  is  to  be  sent  to  another  place, 
it  is  cut  off.  In  the  charcoal  forge,  such  bars  are  to  be  welded  to 
every  small  lump  of  iron  designed  to  be  drawn  into  any  specific 


340  MANUFACTURE    OF  IRON. 

form.  In  puddling  establishments,  these  bars  are  troublesome,  and 
occasion  loss  of  iron,  such  as  that  wasted  in  heating  the  bars ;  this 
heating  is  generally  done  in  the  fire  grate  of  the  puddling  furnace, 
and  not  unfrequently  in  the  back  of  the  flue.  In  well-conducted 
establishments,  this  iron  is  rolled  directly  from  the  blooms  in  the 
roughing  rollers,  in  which  a  couple  of  grooves  are  expressly  made 
for  that  purpose.  The  puddlers  are  required  to  make  their  own  rods. 
The  disadvantages  connected  with  this  system  gave  rise  to  many 
attempts  to  shingle  with  tongs;  but  these  were  attended  with  little 
success  at  the  T  hammer.  At  the  steam  hammer,  tongs  may  be 
used  without  difficulty ;  the  hammer  is  perfectly  in  the  power  of  the 
hammerman.  At  the  T  hammer,  this  is  the  main  difficulty  to  be 
overcome. 

g.  The  faces  of  hammers  and  anvils  are  of  various  shapes ;  but 
the  principle  on  which  they  are  constructed  is,  that  they  should  be 
more  or  less  broad,  according  to  the  width  of  the  hammer.  Too 
small  a  face  cuts  the  iron  too  much,  and  a  very  broad  face  works  too 
slowly.  In  small  hammers,  the  face  varies  from  one  and  a  half  to 
four  inches  in  width;  and  the  face  of  the  T  or  steam  hammer  should 
be  at  least  five  inches  broad.  The  anvil  and  hammer  face  of  a 
steam  or  T  hammer  is  almost  a  square  plate,  twenty  inches  in 
length,  and  sixteen  in  width.  For  shingling,  this  would  be  too 
large;  therefore,  a  face  an  inch  in  height  is  raised  in  the  middle  of 
the  plate,  and  runs  across  the  plate  in  a  direction  opposite  to  the 
workman.  In  addition  to  this,  a  second  face  is  raised  on  the  half 
of  the  anvil,  running  at  right  angles  to  the  first.  This  serves  for 
stretching  or  drawing.  Fig.  100  shows  the  arrangement  for  shin- 
Fig,  ioo. 


Hammer  faces  to  a  T  hammer. 


gling  blooms.     The  cross  face  b  is  generally  extended  to  both  sides 
when  the  machine  iron  is  forged. 


FORGING  AND  ROLLING. 


341 


Many  manufacturers  prefer  hammers  to  other  means  of  forg- 
ing iron.  Experience  does  not  establish  the  wisdom  of  this  pre- 
ference. Good  iron  is  good  everywhere,  and  under  all  circum- 
stances ;  and  the  hammer  does  not  make  it  better.  Nevertheless, 
the  hammer  has  one  advantage.  Inferior  workmen  dread  it,  because 
it  breaks  badly  worked  iron  more  readily  than  any  other  machine. 
In  the  charcoal  forge,  it  smashes  raw  iron ;  and  in  the  puddling 
works,  it  crumbles  those  balls  which  have  been  carelessly  put  to- 
gether. Honest  workmen,  who  do  their  duty,  and  work  their  iron 
well,  are  not  afraid  of  it ;  nor  is  their  iron,  compressed  by  any 
method,  inferior  to  that  shingled  by  the  hammer.  The  quality  of 
the  iron  is  determined  in  the  forge ;  and  neither  the  hammer  nor 
the  rollers  have  any  essential  influence  upon  it. 

II.  Squeezers. 

a.  Squeezers,  or  machines  which  condense  a  ball  by  pressure,  have 
been  employed,  and,  in  most  instances,  have  fulfilled  the  design  of 
their  construction.  From  experiments  made,  it  is  evident  that  good 
squeezers  work  as  well  as  the  best  hammers.  No  difference  in  the 
quality  of  the  iron  subjected  to  the  action  of  either  is  perceptible. 
In  preference  to  other  forms,  we  present  a  drawing  of  a  New-Fug- 
land  lever  squeezer,  which  is  of  simple  construction.  Fig.  101  c: 

Fig.  101. 


Squeezer, 

hibits  it  in  vertical  section.     This  machine  is  cheap  and  durable, 
and  will  squeeze  100  tons  of  iron  per  week.     The  illustration  so 


342  MANUFACTURE   OF  IRON. 

clearly  represents  the  whole  machine,  that  a  specific  description  of 
it  is  unnecessary.  The  bed  plate  a  is  cast  in  one  piece;  it  is  six 
feet  long,  fifteen  inches  wide,  and  twelve  inches  high.  The  whole 
is  screwed  down  on  a  solid  foundation  of  stone,  brick,  or  timber ; 
the  first  is  preferable,  b  is  the  movable  part,  which  makes  from 
eighty  to  ninety  motions  per  minute.  The  motion  is  imparted  by 
the  crank  0,  which  in  turn  is  driven  by  means  of  a  strap  and  pul- 
ley by  the  elementary  power.  The  diameter  of  the  flywheel  is  from 
three  to  four  feet.  The  anvil  d  is  about  two  feet  in  length,  and 
from  twelve  to  fourteen  inches  in  width;  it  is  a  movable  plate,  at 
least  three  inches  thick,  which,  if  injured,  can  be  exchanged  for 
another.  The  face  of  the  working  part  of  the  lever  exactly  fits  the 
anvil,  and  consists  of  plates  attached  by  means  of  screws.  It  is 
desirable  to  have  all  these  face  plates  in  small  parts  of  eight  or  ten 
inches  in  width.  By  this  means,  they  are  secured  against  breaking 
by  expansion  and  contraction.  The  whole  machine,  including 
the  crank  and  everything,  is  made  of  cast  iron,  and  will  weigh  four 
or  five  tons. 

For  the  compression  of  puddled  balls,  these  squeezers  are,  as  we 
have  stated,  quite  as  serviceable  as  the  best  T  hammer,  or  any  other 
hammer.  But  for  the  reduction  of  charcoal  iron,  they  have  either 
not  been  tried,  or  they  are  insufficient.  If  the  former,  we  would 
advise  the  experiment,  confident  that  no  difficulty  will  occur,  pro- 
vided the  machine  is  sufficiently  strong  to  resist  the  reaction  of  the 
hard  and  cold  bloom.  Charcoal  iron  is  generally  harder  than  pud- 
dled iron,  and  a  stronger  machine,  therefore,  is  required  to  compress 
it.  Still,  there  is  no  doubt  that  the  squeezer  will  answer  excellently, 
so  far  as  the  shingling  of  blooms  is  concerned.  Whether  it  is  ap- 
plicable to  the  drawing  of  bars  is  a  question  which  experiment  alone 
can  decide.  Should  its  adaptation  be  proved,  and  should  the 
squeezer  supplant  the  hammers  of  the  charcoal  forge,  we  believe 
that  it  would  be  the  most  useful  improvement  which  could  be  added 
to  the  machines  for  forging  iron.  The  imperfection  of  the  lever 
squeezer  is  its  liability  to  wear  out  at  the  fulcrum,  and  in  the  brass 
boxes  of  the  crank  shaft  and  connecting  rod.  The  motion  of  the 
outer  points  of  the  working  part  seldom  extends  beyond  four  inches, 
and  frequently  less.  If  a  separate  place  for  upsetting  the  blooms 
is  made  at  the  face,  but  little  stroke  is  needed ;  but  if  no  such  off- 
set is  appended,  a  higher  lift  is  necessary. 

b.  One  of  the  most  useful  machines — labor-saving  machines — 
with  which  we  are  acquainted,  is  Burden's  rotary  squeezer.  This 
is  an  American  invention.  It  includes  the  fundamental,  distinctive 


FORGING   AND  ROLLING. 


343 


element  of  a  perfect  machine,  that  is,  rotary  motion.  Experience 
has  proved  this  to  be  a  highly  useful  squeezer,  and  it  is  now  in  a 
fair  way  of  supplanting  all  those  machines  by  which  puddled  balls 
are  condensed  into  blooms.  Many  of  the  Eastern  manufacturers 
employ  it,  and  at  the  Western  mills  it  appears  to  be  quite  a  favorite. 
At  Pittsburgh,  it  is  found  in  almost  every  establishment.  Fig.  102 

Fig.  102. 


Rotary  squeeze?. 

exhibits  it  in  vertical,  and  Fig.  103  in  horizontal,  section.     The 
whole  apparatus  is  of  cast  iron,  and  very  strong  and  heavy,  which, 

Fig.  103. 


Ground-plan  of  the  rotary  squeezer. 

as  a  matter  of  course,  is  indispensable.     Our  illustrations  are  de- 
signed simply  to  convey  a  general  idea  of  the  machine.     As  the 


344  MANUFACTURE   OF  IRON. 

machine  is  patented,  those  only  can  use  it  who  obtain  permission 
from  the  inventor.  The  stationary  part  of  the  apparatus  is  marked 
a,  a,  a ;  this  consists  chiefly  of  a  cast  iron  cloak,  which  encloses 
the  movable  parts  5,  5,  b.  An  excentric  space  between  the  two 
main  parts  is  thus  left,  in  which  the  ball  is  formed  into  a  bloom. 
The  ball  is  inserted  at  <?,  moves  round,  and  appears  at  c?,  a  well- 
formed  bloom.  A  few  seconds  are  sufficient  to  accomplish  this  con- 
densation. When  the  machine  first  appeared,  a  doubt  was  entertain- 
ed whether  it  could  duly  accomplish  the  upsetting,  that  is,  squeeze 
the  bloom  lengthwise;  but  no  difficulty  appears  to  exist  where  the 
balls  are,  as  nearly  as  possible,  of  equal  size.  Besides,  the  top 
e  is  movable,  sliding  up  and  down;  but  this  motion  is^very  slight. 

At  the  double  puddling  furnace,  this  squeezer  at  once  enables  us 
to  overcome  a  serious  difficulty,  namely,  the  loss  of  time  and  iron 
occasioned  by  the  slower  work  of  the  T  hammer  and  the  lever 
squeezer.  If  the  roughing  rollers  are  in  such  condition  as  to  draw 
as  fast  as  the  squeezer  forms  blooms,  a  few  minutes  are  sufficient  to 
work  off  a  heat  of  800  pounds.  This  is  one  great  advantage.  The 
other  advantages  are  that  two  workmen  less  are  needed,  and  a  great 
deal  of  repair  and  frequentjlisturbances  obviated.  In  the  working 
of  the  iron,  hammers  are  unnecessary,  because  they  do  not  improve 
it  directly.  Well-worked  iron,  put  directly  into  the  rough  rollers, 
without  shingling,  is  not  in  the  least  degree  inferior  to  that  shingled 
by  the  T  hammer.  Hammers  are  but  imperfect  machines,  the  re- 
mains of  an  elementary  knowledge  of  engineering ;  and  the  sooner 
they  are  superseded  by  better  implements  of  workmanship,  the 
better. 

III.  Roughing  Rollers. 

The  shingled  blooms  are  conveyed  directly  from  the  squeezer  or 
hammer  to  the  rollers,  commonly  called  rough  rollers.  In  some  parts 
of  Europe,  no  hammers  or  squeezers  are  employed;  but  the  balls  are 
taken  directly  from  the  puddling  furnace  to  the  rollers,  which  have 
large  grooves,  and  in  the  first  and  second  groove  projecting  ribs,  for 
catching.  In  this  country,  no  such  rollers  are  used.  We  do  not 
find  any  difference  in  the  quality  of  the  iron,  whether  shingled  or 
put  through  the  rollers  directly  from  the  furnaces,  except  that  aris- 
ing from  the  inability  of  the  latter  to  effect  the  compression  of  the 
bloom  lengthwise ;  this  causes  a  waste  of  iron  in  the  re-heating  fur- 
nace, because  the  rough  bars  are  never  so  sound  at  the  edges  and 
the  ends  as  those  made  from  shingled  or  squeezed  blooms.  For  this 


FORGING  AND  ROLLING. 


345 


reason,  it  is  preferable  to  shingle  the  balls,  or  to  form  sound  blooms 
by  some  method  before  the  iron  is  taken  to  the  rollers. 

The  limited  size  of  the  engraving  does  not  permit  us  to  give 
such  detailed  views  of  the  machinery  as  we  would  desire  to  give ; 
still,  we  shall  endeavor  to  make  the  subject  as  clear  and  compre- 
hensible as  possible.  Fig.  104  shows  a  side  view  of  a  roughing 

Fig.  104. 


Roughing  rollers,  and  foundation  of  timber. 

train.  Any  row,  or  more  than  one  set  of  rollers,  is  called  a  train. 
The  upper  part  above  the  sill  «,  is  all  made  of  cast  iron.  The  part 
below  a  is  the  foundation  below  ground,  and  is  here  assumed  to  be 
a  framework  of  timber.  In  most  of  our  rolling  mills,  the  founda- 
tion of  a  train  is  made  of  timber,  and  answers  well  enough  for  a 
temporary  purpose.  Timber  lasts  but  a  short  time.  Good  substan- 
tial works  ought  to  have  stone  or  brick  foundations ;  these  are  not  only 
more  durable,  but  preserve  the  machinery  by  their  greater  stability: 
the  machinery  works  more  quietly,  and  does  not  make  so  much 
noise  as  when  built  upon  a  wooden  frame.  At  b  are  two  standards, 
carrying  two  cogwheels.  These  wheels  are  nearest  to  the  steam- 
engine  and  the  flywheel.  They  have  the  diameter  of  the  rollers, 
in  the  dividing  line,  and  serve  to  conduct  the  motion  from  the  mov- 
ing power  to  the  rollers,  giving  the  top  rollers  a  motion  independent 
of  the  bottom  rollers.  They  are  sometimes  put  close  to  the  first  set 
of  rollers,  forming,  at  the  same  time,  the  coupling  boxes  c\  or  they 


346  MANUFACTURE   OF   IRON. 

are  fastened  to  the  rollers  at  d,  and  conduct  the  motion  back.  Such 
arrangements  are  very  imperfect;  the  first  is  troublesome,  because 
the  wheels  do  not  stick  to  the  rollers — the  expansion  and  contrac- 
tion caused  by  the  heat  of  the  rollers  unfasten  all  filling  between  the 
wheel  and  the  roller,  or,  if  too  close  fitted,  break  the  wheel.  Fast- 
ening the  wheel  at  d  is  equally  bad,  for  then  the  coupling  boxes  be- 
tween the  top  rollers  break  so  frequently  as  to  cause  disturbance. 
The  motion  from  the  wheels  b  is  conducted,  by  means  of  the  cou- 
pling rods  e  0,  to  the  rollers  /;  e  e  are  cast  iron  spindles  two  or  two 
and  a  half  feet  in  length,  joined  to  the  rollers  by  the  coupling  boxes 
c.  The  coupling  boxes  g  are  frequently  cast  in  one  piece  with  the 
rod,  to  make  it  stronger,  /exhibits  the  roughing  rollers ;  these  take 
the  bloom,  and  draw  or  reduce  it  into  billets  of  greater  or  less  size, 
according  to  the  size  of  the  flat  bars  intended  to  be  drawn.  For  the 
making  of  hoops,  nail  rods,  and  fancy  rods  less  than  half  an  inch 
square,  the  billets  are  reduced  to  an  inch  or  an  inch  and  a  half 
square,  and  taken  to  the  re-heating  furnace,  to  be  directly  converted 
into  merchant  iron. 

a.  Billets  from  the  roughing  rollers  have  to  serve  for  square,  round, 
and  flat  iron;  in  fact,  the  condensation  and  drawing  of  the  iron  are 
principally  effected  by  the  roughing  rollers.  For  this  reason,  the 
grooves  are  not  square,  but  their  form  is  that  of  a  section  between 
a  circle  and  a  square.  This  form  is  shown  by  Fig.  105.  The 

Fig.  105. 


Grooves  in  roughing  rollers. 

grooves  are  a  little  shorter  in  the  vertical  than  in  the  horizontal  direc- 
tion ;  that  is,  the  vertical  is  shorter  than  the  horizontal  diagonal.  The 
hot  iron,  in  being  worked  through  these  rollers,  is  turned  one  quar- 
ter at  each  groove,  which  secures  sound  edges  in  the  billets.  The 
bloom,  in  this  first  operation,  is  never  so  reduced  as  to  become  less 


FORGING  AND  ROLLING.  347 

than  an  inch  or  an  inch  and  a  quarter  billet.  The  first  groove, 
which  receives  the  bloom,  is  to  be  sufficiently  large  to  catch,  for  which 
purpose  six  inches  are  in  most  cases  a  good  size ;  at  least,  a  larger 
size  is  seldom  required  for  forge  and  puddled  blooms.  The  degree 
of  condensation,  in  these  rollers,  from  one  groove  to  the  other  (the 
decrement),  is  in  the  proportion  of  the  squares  of  eleven  to  fifteen, 
or  nearly  one-half;  that  is  to  say,  the  original  length  of  the  bar  is 
nearly  doubled  in  each  groove.  To  reduce  a  bar  from  six  inches 
to  one  inch  square,  we  require  seven  grooves,  measuring  respect- 
ively 6, 4|,  3£,  2f  inches,  and  If,  If,  1  inch ;  a  roller  forty  inches 
long  will  thus  be  needed,  if  one  inch  between  each  groove  is  left. 
This  proportion  of  decrement  answers  well  for  soft  and  puddled  iron, 
and  good,  strong  rollers ;  but  for  hard  and  sound  puddled  iron,  it 
condenses  too  rapidly.  Charcoal  iron  it  will  work  with  difficulty. 
In  these  cases,  it  is  advantageous  to  condense  less  and  take  more 
grooves.  Fifteen  to  twelve  is  a  good  proportion  ;  condensation  less 
than  that  is  seldom  required.  For  this  purpose,  nine  grooves — mea- 
suring respectively  6, 4f ,  3f ,  3,  2f  inches,  and  lT9o,  1 J,  l£,  1  inch, 
requiring  a  roller  forty-six  inches  long — are  needed.  Roughing  roll- 
ers, if  made  of  good  strong  cast  iron,  can  be  seven  feet  long ;  the 
remaining  three  feet  ten  inches  may  serve  for  flat  grooves.  This 
plan  is  generally  followed,  and  is  well  adapted  for  castings  made 
from  Baltimore  or  Hanging  Rock  pig  iron.  But  for  castings  from 
anthracite  or  coke  iron,  it  is  not  advantageous  to  use  rollers  of  such 
length.  Where  the  first  cost  is  no  object,  it  is  advisable  to  make 
two  sets  of  rollers  for  roughing;  to  take  one  set  for  billets,  the 
other  for  flat  bars.  In  large  and  well-organized  establishments,  this 
plan  is  generally  pursued ;  it  has  the  advantage  that,  should  any 
accident  happen,  which  is  mostly  with  the  flat  rollers,  the  works 
need  not  necessarily  be  stopped,  for  it  very  seldom  happens  that 
anything  goes  wrong  at  the  billet  rollers. 

b.  Where  two  sets  of  roughing  rollers  are  used,  the  second  set  #  is 
generally  as  long  as  the  first,  and  coupled  by  spindles  and  boxes  to 
the  first.  These  rollers  have  flat  grooves  only,  and  make  flat  bars 
from  one-half  to  three-quarters  of  an  inch  thick,  and  from  two  to 
six  inches  wide.  Grooves  of  these  dimensions  cannot  be  cut  into 
one  pair  of  rollers ;  and,  if  a  variety  of  width  in  the  rough  bars  is 
required,  two  or  more  sets  of  flat  rollers  are  generally  required. 
Rough  bars  six  inches  in  width,  and  those  two  inches  in  width,  are 
seldom  needed ;  but  where  certain  dimensions  of  rod  iron  of  greater 
or  less  width  are  constantly  made,  such  as  railroad  iron  or  hoops, 


348  MANUFACTURE   OF   IRON. 

rough  bars  are  of  advantage.  But  this  is  of  little  consequence, 
and  rough  bars  3j,  4,  or  4J  inches  wide,  and  from  J,  |,  to  f  of 
an  inch  thick,  are  most  commonly  used.  The  first  groove  which 
receives  the  square  bloom  is  the  narrowest  and  highest ;  as  the 
grooves  diminish  in  height,  they  increase  in  width.  The  last 
would  not  be  actually  needed,  were  it  not  for  the  catching  of 
the  bar  by  the  rollers ;  but  it  is  advisable  to  make  it  as  small  as  pos- 
sible. The  edges  of  a  flat  bar  become  less  sound  and  fibrous,  if  the 
breadth  of  the  grooves  increases  too  fast.  For  the  better  compre- 
hension of  the  subject,  we  will  furnish  a  practical  illustration,  and 
annex  a  set  of  rollers,  forty-six  inches  long,  with  grooves  for  bars 
four  inches  wide.  The  thickness  can  be  altered  by  screwing  the  top 
roller  upward  or  downward.  Fig.  106  represents  a  set  of  rollers, 

Fig.  106. 


Flat  rollers. 

which,  if  of  good  cast  metal,  are  fourteen  inches  in  diameter,  that 
is,  from  centre  to  centre,  which  of  course,  in  this  case,  makes  the 
bottom  roller  very  strong.  In  the  billet  rollers,  both  diameters  are  the 
same.  The  first  groove,  marked  a,  is  the  finishing  groove ;  therefore, 
it  is  four  inches  wide,  and  three-fourths  of  an  inch  thick.  If  now 
we  increase  in  the  ratio  of  from  12*  to  152,  which  is  nearly  2  :  3, 
the  next  groove  is  to  be  1J  inch,  or  a  little  less,  high,  and  at  least 
y^th,  better  Jth,  of  an  inch  narrower.  The  next  groove  will  be  If 
by  3f  ;  then  2J  by  3| ;  then  3J  by  3j.  The  last  groove  is  unne- 
cessary, for  it  is  a  square,  and  will  not  take  a  billet  of  larger  size 
than  3j  inches.  Here  we  have  four  grooves,  which,  if  we  leave  Ij 
inch  collar  between  them,  and  two  inches  for  the  end  collar,  will 
take  2  +  4+lJ  +  3S  +  li  +  3f  +  lJ  +  3f  +  lin=23j  inches.  This 
is  not  more  than  half  the  length  of  the  roller ;  and  the  other 


FORGING  AND   ROLLING. 


349 


half  may  be  arranged  for  a  -wider  or  a,  narrower  bar.  The  bottom 
or  ground  of  the  grooves  in  the  bottom  roller  is  not  quite  square;  the 
corners  in  both  sides  are  left  standing;  instead  of  cutting  the  collar 
square  down  to  the  ground  of  the  groove,  it  is  somewhat  slanted,  and 
a  quarter  of  an  inch  in  the  corner  is  left  remaining.  These  round 
corners  in  the  bottom  roller  squeeze  the  corners  of  the  rough  bars, 
whereby  they  become  more  sound,  and  diminish,  in  consequence, 
the  waste  of  iron  in  the  re-heating  furnace.  Rough  rollers  gene- 
rally make  from  thirty  to  forty  revolutions  per  minute  ;  this  motion 
is  sufficient  where  single  furnaces  and  T  hammers  are  in  use,  but 
it  is  too  slow  for  double  furnaces  and  rotary  squeezers. 

c.  Fig.  107  shows  a  vertical  section  through  the  rollers  and  foun- 
dation, and  a  view  of  the  housing  frames,  in  which  the  rollers  are 

Fig.  107. 


View  of  a  housing,  and  section  of  rollers  and  foundation. 

supported.  The  housing  a  is  a  heavy  frame  of  cast  iron,  being 
frequently  ten  by  twelve  inches  square  in  the  pillars,  if  designed 
for  heavy  bar  or  sheet  iron.  For  merchant  bar  eight  by  ten,  for 
small  bar  six  by  eight,  and  for  wire  five  by  six  inches  is  sufficiently 


350  MANUFACTURE   OF  IRON. 

strong,  even  though  the  metal  is  not  of  the  very  best  quality.  The 
width  between  the  two  pillars  must  correspond  to  the  diameter  of  the 
rollers.  Short  rollers  of  good  metal  are,  when  of  fifteen  or  sixteen 
inches  in  diameter,  sufficiently  strong;  but  long  rollers,  or  rollers  of 
weak  metal,  must  be  at  least  seventeen  or  eighteen  inches.  If  the 
roughing  rollers  are  eighteen  inches  in  diameter,  then  the  lowermost 
of  the  flat  rollers  will  be  at  least  three  inches  larger,  which  will  bring 
the  housings  to  twenty-two  inches ;  adding  one  inch  space,  twenty- 
three  inches  will  be  the  distance  between  the  uprights.  In  common 
cases,  five  feet  are  a  sufficient  height  for  housings,  and  for  railroad 
iron  or  sheet  iron  alone  are  a  few  inches  more  required.  The  wrought 
iron  screw  b  is  generally  four  and  a  half  inches  in  diameter,  and 
moves  in  a  brass  box,  which  is  hexagonal  and  a  little  tapered,  so  as 
to  fit  very  tight  into  the  cast  iron  top.  The  thread  of  the  screw  is  a 
square  from  one-fourth  to  three-eighths  of  an  inch  in  size,  so  that  one 
revolution  of  the  screw  amounts  to  one-half  or  three-fourths  of  an 
inch.  The  screw  presses  upon  the  cast  iron  safety-cap  <?,  which 
is  calculated  to  break  before  any  other  part  of  the  machinery ;  and 
the  rollers,  housings,  &c.,  are  thus  secured  against  accidents.  The 
cap  d  is  of  cast  iron,  lined  with  brass  boxes,  and  these  brass  boxes 
are  frequently  lined  with  hard  lead  or  type  metal.  This  cap,  as  well 
as  its  bottom  part  e,  slides  on  both  sides  in  the  housing,  either  in 
triangular  or  square  grooves.  Housings  for  roughing  rollers  are  fre- 
quently found  to  be  of  a  simple  construction,  and  the  sliding  motion 
of  the  boxes  is  guided  by  a  triangular  prism,  which  gives  to  the  cap 
F.  log  the  form  shown  in  Fig.  108  ;  this,  how- 

.ever,  is  not  the  very  best,  and  does  not 
work  well  enough  for  square  and  round 
merchant  bar.  The  two  screws  /,  /, 
Fig.  107,  regulate  the  height  of  the  top 
roller  by  means  of  the  plummer  block 
e.  These  screw  bolts  pass  through  the 
cap  d.  The  wrench  g  serves  to  lower 

Triangular  prism  and  cap.  an(j  raige  tne  top  roHer?  go  ag  to  increase 

or  diminish  the  space  between  the  two  rollers,  h  is  a  cast  iron 
plate,  called  an  apron,  on  the  side  where  the  hot  iron  enters  the 
rollers  ;  it  is  simply  a  plate  filling  the  space  between  the  housings, 
and  joining  the  bottom  roller,  so  as  to  form  a  bench  on  which  the 
iron  may  rest.  On  the  opposite  side  Jc,  is  a  similar  apron,  if  rough- 
ing rollers ;  it  is  somewhat  lower  than  the  other,  and  its  inner  edge 
fits  into  the  triangular  grooves  of  the  bottom  roller,  so  as  to  scrape 


FORGING  AND  ROLLING. 


351 


off  any  pieces  of  iron  which  fall  loose  from  the  bloom,  or  which 
stick  to  the  roller.  The  fitting  of  this  apron  to  the  roller  is  some- 
what difficult,  and  it  is  a  preferable  plan,  instead  of  casting  the 
scrapers  to  the  plate,  to  form  a  straight  edge,  the  apron  somewhat 
smaller,  and  screw  the  scrapers  to  the  plate,  which  then  may  be 
made  of  wrought  iron.  The  screw  bolts  i,  i  serve  to  steady  the 
housings,  and  secure  the  close  fitting  of  the  boxes  to  the  rollers. 

If  flat  bar  rollers,  railroad,  or  fancy  iron  rollers   are  in  the 
housings,  a  different  arrangement  with  respect  to  scrapers  must  be 
followed.     Eig.  109  shows  a  section  of  a  set  of  flat  bar  or  rail- 
Fig.  109. 


Section  of  rollers  and  foundation. 

rollers.  Instead  of  the  apron,  there  is  only  a  square  bar  of  wrought 
or  cast  iron,  upon  which  wrought  iron  scrapers,  £,  having  the  form 
of  wedges,  rest.  These  wedges  are  of  the  size  of  the  grooves  in  the 
roller,  and  fit  loosely  into  the  grooves  with  their  edges.  Besides 
the  scrapers,  there  is  a  second  set  below,  b,  called  guards.  These 
guards,  marked  e,  are  wrought  iron  wedges,  resting  in  a  strong  cast 


352  MANUFACTURE   OF   IRON. 

iron  grooved  bar  d.  In  this  drawing,  we  see  a  different  arrange- 
ment, with  respect  to  the  screw  bolts  /  /,  from  that  shown  in  Fig. 
107.  The  nuts  of  the  screws,  instead  of  resting  on  the  top  of  the 
housings,  rest  on  a  plate  of  wrought  iron  e,  e,  which  plate  is  fitted 
upon  a  round  collar  and  the  neck  of  the  screw,  and  follows  the 
screw  in  its  upward  and  downward  motion.  This  plan  is  preferable 
to  any  other,  for  it  keeps  the  top  roller  always  closely  fitted  in  the 
plummer  blocks,  whereas,  by  the  method  shown  in  Fig.  107,  the 
top  roller  is  loose,  and  frequently  opposed  to  breaking.  The  ar- 
rangement here  exhibited  is  well  adapted  for  flat  bar,  rail,  and  heavy 
sheet  iron  rollers,  or  in  all  cases  where  the  top  roller  is  moved  by 
pinions.  We  find,  in  Fig.  109,  also  a  different  arrangement  with 
respect  to  fastening  the  housings  upon  the  foundation ;  this  is  ef- 
fected by  screwing  the  housings  to  the  bed-plate  #,  which  bed-plate 
is  fastened  to  the  foundation  by  separate  screws.  On  the  bed-plate 
are  two  projecting,  prismatic  ribs,  which  fit  in  corresponding  notches 
in  the  housings.  By  these  means,  the  latter  are  kept  in  a  straight 
line,  and  there  is  no  difficulty  in  keeping  a  train  in  good  order. 
The  foundation  is  assumed  to  be  of  stones  or  brick,  at  least  from 
eight  to  nine  feet  deep.  In  our  illustration,  this  proportional  depth 
is  not  exhibited. 

d.  The  connection  between  the  motive  power  and  the  rollers  is 
effected  simply  by  a  strong  coupling  box,  that  is,  if  the  train  is  always 
connected  with  the  engine ;  but  if  the  motive  power  serves  for 
different  trains,  or  different  machinery,  another  connection,  which 
permits  the  stopping  of  the  train,  is  to  be  made  use  of.  Such  a 
joint,  or  cam  box,  is  represented  by  Fig.  110  ;  the  part  a  is  a  box 

Fig.  110. 


Cam  box,  coupling  box. 


movable  upon  the  junction  shaft  5,  by  means  of  an  iron  fork  rest- 
ing on  the  collar  <?,  or  a  simple  lever  bar,  playing  in  the  groove. 
The  form,  or  section  of  the  junction  shaft  b,  and  junction  shafts 


FORGING  AND   ROLLING.  353 

generally,  varies.  Some  manufacturers  employ  simply  square  rods, 
others  round.  This  is  an  object  of  some  importance ;  because,  if 
the  junction  shafts  are  not  of  the  right  form  or  strength,  the  rollers 
are  very  soon  made  useless :  the  junction  is  so  far  injured  as  to 
break  the  coupling  boxes,  and  occasion  other  accidents.  A  simply 
square  section  of  the  junction  is  not  the  best  form.  Experience  has 
determined  that  the  cross  section,  represented  by  Fig.  Ill,  is,  of 
all  others,  the  most  practical.  The  coupling  boxes,  on  the  junc- 
tion shafts  between  the  rollers,  are  kept  in  their  places  by  four 
wooden  sticks ;  these,  filling  the  four  corners  of  the  shaft,  are  kept 
together  by  leather  straps,  as  represented  in  Fig.  112.  The  strength 
Fig.  ill.  Fig.  112. 


Section  of  a  junction  Junction  shaft  and  coupling  boxes, 

shaft,  wood  filling, 
and  leather  strap. 

of  these  junction  shafts  varies  according  to  the  size  of  the  rollers 
to  which  they  are  to  be  applied.  We  find  them  from  ten  to  twelve 
inches  in  diameter  for  sheet  iron  rollers,  in  which  case  hard  rollers 
with  polished  surfaces  are  at  work ;  from  eight  to  ten  inches  for 
common  sheet  iron  and  railroad  iron  rollers ;  five  to  six  inches  for 
merchant  iron  rollers  ;  and  from  three  to  four  inches  for  wire  and 
small  rod.  The  quality  or  strength  of  the  metal  from  which  rollers, 
boxes,  and  shafts  are  cast,  must  of  course  determine  the  dimen- 
sions of  the  junction  shafts. 

e.  Doubts  are  frequently  expressed  as  to  the  propriety  of  working 
several  trains  of  rollers  by  one  flywheel.  In  the  Western  works, 
but  one  flywheel  is  commonly  employed,  namely,  the  flywheel  be- 
longing to  the  steam-engine,  which  is  generally  somewhat  heavier 
than  the  ordinary  flywheel.  This  plan  works  well.  Some  of  the 
Eastern  works  employ  a  flywheel  at  each  train,  but  with  what  ad- 
vantage we  cannot  see.  This  much  is  certain,  that  several  fly- 
wheels attached  to  the  same  power,  and  moving  in  opposite  direc- 
tions, cause  more  breakage  than  one  flywheel  will  cause.  There  is 
no  necessity  whatever  for  more  than  one  flywheel,  where  there  is 
but  one  engine,  and  the  excuse  for  employing  such  is  only  to  be 
found  in  a  deficiency  of  power,  which,  in  iron  works,  is  one  of  the 
23 


354  MANUFACTURE   OF  IRON. 

greatest  faults  that  can  be  committed.     We  shall  speak  of  this 
subject  hereafter. 

IV.  Merchant  Mill. 

a.  For  the  making  of  wire,  or  small  bar  iron  less  than  one  inch 
square,  or  round,  small  hoops  less  than  two  inches  wide,  three 
rollers,  one  over  the  other,  forming  a  set,  and  generally  three  sets  a 
train,  are  required.  Fig.  113  shows  a  section  of  such  a  train  through 

Fig.  113. 


SBlw^^ 

Merchant  rollers  for  small  iron. 

a  brick  foundation,  and  a  view  of  the  rollers,  a  shows  the  union 
standards  and  pinions,  of  which  there  are  three ;  the  power  is  con- 
nected with  the  lower  wheel :  b  the  roughing  rollers,  c  the  merchant 
rollers,  and  d  hard  rollers.  The  rollers  b  are  never  changed,  and 
contain  such  grooves  as  will  take  the  heaviest  pack  or  pile  neces- 
sary for  small  iron,  which  is  seldom  more  than  forty  or  fifty  pounds. 
Rough  bars  three  and  a  half  inches  wide,  and  twelve  inches  long, 
forming  a  square  pile,  will  make  such  a  pack.  The  first  groove 
must  be  three  inches  square,  which  makes  a  roller  of  ten  inches  in 
diameter  necessary.  Commonly,  rollers  but  eight  or  nine  inches  wide 
are  used  for  this  train,  in  which,  of  course,  nothing  heavier  than 
one  inch  bars  can  be  made ;  the  first  groove  then  measures  two 
or  two  and  a  half  inches,  for  which  reason  small  rough  bars,  or 
billets,  are  required.  The  length  of  the  rollers  is  seldom  more  than 
three  feet,  even  if  they  are  of  large  diameter;  in  the  present  case, 
it  is  of  no  use  to  have  long  rollers.  The  merchant  rollers  c-  are 
arranged  either  for  square,  round,  or  flat  bars.  A  construction  of 
the  housings  is  shown  in  Fig.  114,  in  which  the  necessary  screws 
for  adjusting  the  rollers  may  be  seen.  As  the  pressure  from  the 
rollers  upon  the  housing  is  not  very  strong,  the  cap  a  is  cast 
as  a  separate  piece,  and  screwed  on  by  bolts ;  it  affords  the  ad- 
vantage of  lifting  the  rollers  out  by  means  of  a  crane,  to  effect 


FORGING   AND  ROLLING. 


355 


which  would  be  otherwise  very  difficult.     The  plummer  blocks  <?,  <?, 
c,  c  are  fitted  in  a  square  groove  in  the  housing,  and  screws  press- 
Fig.  114. 


Section  of  merchant  rollers. 


ing  from  behind  keep  blocks,  and  consequently  rollers,  in  their  pro- 
per place,  which  is  necessary,  if  round  or  square  iron  is  to  be  made. 
This  arrangement  is  more  clearly  shown  in  Fig.  115,  where  c,  c 


Fig.  115. 


Roller  guards. 

are  the  screws  pressing  behind  the  plummer  block,  and  of  course 
move  the  roller  lengthwise,  if  turned  on  both  ends  in  opposite 


356  MANUFACTURE   OF   IRON. 

directions.  In  this  figure,  flat  rollers  are  shown,  with  a  view  of 
the  scrapers  from  above.  Upon  these  rollers,  a  current  of  cold 
water  is  directed,  divided  into  small  streams.  This  cooling  tends 
to  preserve  the  rollers ;  but  it  is  applied  mainly  for  the  purpose 
of  preventing  the  hot  iron  from  sticking  to  them,  which  is  not  only 
very  troublesome,  but  causes  breakage,  and  ought,  therefore,  by 
all  means  to  be  avoided. 

b.  If  square  or  round  iron  is  to  be  made,  then,  instead  of  the 
common  aprons,  guides,  e,  e,  Fig.  114,  are  set  before  the  rollers. 
These  are  not  so  much  required  for  square  or  flat  iron ;  but  they  are 
very  much  needed  in  making  round  iron.     A  piece  of  iron,  of  the 
form  of  a  frame,  is  fitted  in  between  the  two  housings,  as  shown  in 
Fig.  113,  e,  and  in  this  frame  the  cast  iron  guides  slide,  being  kept 
in  their  places  by  wedges  or  screws.     These  guides  serve  to  direct 
the  bar  to  that  groove  at  which  it  is  required,  and,  in  the  mean 
time,  to  prevent  the  turning  of  the  rod.     The  guides  and  frame 
are  made  of  cast  iron. 

c.  Smooth  hard  rollers,  twelve,  frequently  twenty  inches  long, 
which  serve  for  polishing  hoops,  are  shown  at  d,  Fig.  113.    It  is  not 
customary  in  this  country  to  make  polished  rod;  but  such  rod  is  fre- 
quently made  in  the  Old  World.     In  this  case,  grooves,  according 
to  the  size  of  the  rod  iron  to  be  made,  are  cut  into  the  rollers.    Such 
iron  very  much  resembles  hammered,  or  charcoal  iron,  and  is  manu- 
factured in  imitation  of  it.     These  hard  rollers  must  be  kept  cool 
by  an  abundant  supply  of  cold  water,  else  their  surface  soon  becomes 
rough,  in  which  case  it  no  longer  polishes.    Hoops  must  be  smooth, 
and,  when  possible,  of  a  uniform  blue  color.     The  smoothness  and 
color  are  increased  by  removing  the  coating  of  scales,  or  hammer-slag, 
which  has  accumulated  in  the  preparatory  rolls  :  this  is  done  by  a 
polisher  or  scraper,  represented  in  Fig.  116,  which  is  an  iron  frame, 

Fig.  116. 


For  cleaning  hoops. 

a,  turning  in  two  necks  at  both  ends,  which  are  attached  to  the 
housings.     A  crank  b,  with  a  handle,  is  at  one  end,  and  serves  to 


FORGING  AND  ROLLING.  357 

turn  the  frame.  If  a  hoop  is  pushed  through  this  frame,  when 
turned  and  opened  to  the  rollers,  it  passes  freely,  but  when  turned 
more  or  less  back,  according  to  its  thickness,  it  is  bent  in  different 
directions,  as  the  dark  line  which  represents  it  indicates.  The 
purpose  of  bending  the  iron  round  such  short  corners  is  to  break  off 
the  scales,  or  hammer-slag.  These  scales  are  an  impure  magnetic 
oxide,  very  brittle  when  cold,  but  fusible  in  a  moderate  heat;  this 
oxide  separates  easily  from  iron,  which  is  not  too  hot.  Therefore, 
the  polishing  will  be  the  more  perfect  the  cooler  the  iron  is,  when 
passed  through  the  hard  rollers.  A  bright  blue  color  is  generally 
preferred  for  hoops.  To  produce  such  a  color,  a  very  pure  but  car- 
bonaceous iron,  or  iron  rendered  cold-short  by  carbon,  is  required. 
If  the  iron,  or  even  the  cinder  in  which  it  has  been  puddled,  con- 
tains any  phosphorus  or  sulphur,  the  surface  of  the  hoops  will  be 
found  cloudy,  and  inclined  to  oxidize  more  highly,  and  turn  red.  A 
large  quantity  of  silicious  cinder  in  the  iron  produces  the  same 
effect.  Good  hoop  iron  is  best  made  in  boiling  furnaces,  from  gray 
pig;  this  pig  iron  is  rolled  into  rough  billets,  and  then  drawn  di- 
rectly into  hoops.  Hoops  made  from  highly  refined  iron,  such  as 
fibrous  charcoal  iron,  or  that  puddled  from  very  good  plate  metal, 
are  very  apt -to  turn  red,  and  are  generally  weak.  The  frame  a  is 
made  as  long  as  the  rollers,  so  as  to  shift  the  working  place  of  the 
rollers,  and  use  gradually  the  whole  surface. 

d.  Where  there  are  three  rollers  in  the  housings,  the  moving  them 
up  and  down  is  not  so  easily  effected  as  where  there  are  but  two, 
and  this  motion  cannot  be  effected  at  all  while  at  work.     The  best 
plan  we  can  adopt  is  to  fit  the  plummer  blocks  well  in  the  housings, 
one  upon  the  other,  and  to  adjust  the  distance  between  the  rollers 
by  means  of  scraps  from  hoops  or  sheet  iron,  or  of  pieces  purposely 
forged.     The  bottom  roller  rests  in  the  housings ;  the  second  or 
middle  one  turns  in  a  movable  plummer  block  resting  upon  the  bot- 
tom of  the  housing.     The  top  roller  rests  in  a  movable  plummer 
block,  and  is  covered  with  a  strong  cap.     The  whole  is  kept  toge- 
ther by  the  top-screw  pressing  upon  the  safety  cap,  as  represented 
in  Fig.  114. 

e.  The  roughing-rollers  are  three  in  number,  and  are  always  of 
the  same  diameter ;  so  also  are  the  rollers  for  square  and  round  bar; 
but  for  flat  iron  or  hoops  the  diameters  of  the  rollers  are,  of  course, 
different.    The  middle  roller  is  the  largest  in  diameter,  and  occupies 
the  place  which  the  bottom  roller  occupies  in  cases  where  but  two 
rollers  are  used.     Fig.  117  shows  the  arrangement.     The  top  and 


358  MANUFACTURE   OF  IRON. 

bottom  rollers  are  of  the  same  size.     The  middle  roller  alone  has 
collars.  The  grooves  in  the  bottom  roller  are  throughout  larger  than 

Fig.  117. 


Grooves  for  flat  iron. 

the  grooves  in  the  upper  roller.  It  is  so  arranged  that,  if  the  first 
groove  in  the  series  is  a,  the  second  is  in  5,  the  third  <?,  fourth  c2,  &c. 
It  is  apparent  that  the  use  of  three  rollers  not  only  augments  their 
durability,  but  saves  time,  fuel,  and  iron.  The  garniture  of  scrap- 
ers and  guards,  described  before,  is  to  be  doubled,  and  applied  to 
different  sides  on  the  middle  and  bottom  rollers. 

f.  For  the  making  of  wire  and  small  hoops,  or  rods  less  than  half 
an  inch,  and  hoops  less  than  one  inch  wide,  the  same  number  of 
rollers  is  employed,  with  this  difference,  that  the  rollers  are  but  four 
and  a  half  or  five  inches  in  diameter.  The  speed  of  rollers  for  mer- 
chant iron  is  generally  from  seven  to  eight  feet  per  second  on  the 
surface,  so  that  the  iron  with  that  speed  will  pass  through  them. 
This  makes,  for  twelve  inch  rollers,  150  revolutions  per  minute, 
and  for  four  inch  wire  rollers,  450  revolutions. 

V.  Heavy  Bar  and  Railroad  Iron  Rollers. 

Iron  heavier  than  that  one  inch  square  is  made  by  rollers  of  larger 
size  than  the  foregoing,  with  but  two  in  the  housings.  For  this  kind 
of  work — to  which  heavy  bar,  locomotive  wheel  tires,  rails,  and  nail 
plates  belong — rollers  from  fifteen  to  twenty  inches  in  diameter 
are  used.  Their  size  depends  upon  the  kind  of  iron  to  be  made ; 
upon  the  quality  of  the  iron  used,  whether  hard  or  soft;  and  upon 
the  quality  of  the  castings  of  which  the  roller  is  made.  A  particu- 
lar description  of  the  making  of  heavy  iron  is  unnecessary,  because 
it  differs  but  slightly  from  the  manipulations  and  principles  with 
which  we  are  already  familiar.  This  may  be  applied  particularly  to 


FORGING  AND  ROLLING.  359 

the  re-heating  furnace.  But,  as  the  making  of  railroad  iron  is  a 
matter  of  particular  interest,  and  as  a  description  of  this  would 
include  all  that  need  be  said  concerning  the  making  of  heavy  bar, 
we  shall  describe  the  process  in  preference  to  any  other. 

a.  The  weight  of  railroad  bars  varies  considerably,  according  to 
section  and  length.  There  are  sections  of  forty  pounds  per  yard, 
and  sections  of  eighty  pounds  per  yard.  In  our  own  country,  rails 
heavier  than  seventy-five  pounds  per  yard  are  not  at  present  in  use; 
the  most  common  are  from  sixty  to  sixty-five  pounds.  A  rail  eight 
yards  long,  which  is  the  common  size,  requires,  therefore,  a  pack  or 
pile  of  from  300  to  500  pounds  of  iron.  Almost  every  railroad  com- 
pany employs  bars  of  a  different  section.  It  is  not  our  province  to 
enter  upon  an  investigation  of  the  construction  of  rail  sections,  for 
the  purpose  of  testing  their  respective  merits;  this  belongs  to  civil 
engineering;  but  we  will  make  a  few  remarks  relative  to  the  manu- 
facture of  different  sections,  so  far  as  this  subject  bears  upon  the 
quality  and  price  of  the  product.  Flat  rails  do  not  differ  in  the 
least  from  common  flat  iron ;  but  if  we  wish  to  make  the  best  article 
from  the  same  material,  it  is  advisable  to  turn  the  bar  in  such  a  way 
into  the  rollers  that  the  joints  of  the  pile  shall  be  vertical  upon  the 
base  of  the  rail;  that  is,  to  run  the  welding  joints  of  the  rough  bars 
through  the  small  section  of  the  rail  bar.  Very  coarse  or  porous 
iron  does  not  make  a  good  rail  in  this  or  in  any  other  way;  it  is 
apt  to  split.  Such  fibrous  iron  may  be  greatly  improved  by  rolling 
the  rough  bars  about  five-eighths  of  an  inch  thick,  and  mixing 
it  with  cold-short  iron.  That  is,  pile  a  bar  of  cold-short  upon 
fibrous  iron,  and  thus  continue  until  the  pile  is  complete;  the  top 
and  bottom  courses  must  be  of  fibrous  iron.  In  this  way  it  works 
exceedingly  well,  and  makes  the  best  and  cheapest  kind  of  rails  that 
can  be  made  from  the  same  material.  The  last  or  finishing  groove 
of  flat  rails  is  generally  provided  with  a  series  of  warts,  in  the  cir- 
cumference of  the  top  roller,  giving  impressions  deep  enough  for 
the  heads  of  spikes.  The  remaining  thickness  of  the  iron  is 
punched  through,  after  the  bar  is  cold. 

Besides  flat  rails,  which  are,  and  will  yet  be  for  a  time  in  use, 
we  find  bridge  rails  employed,  which  have  the  form  of  a  reversed 
U.  We  find  these  with  parallel  sides  like  the  JQ_,  or  with  sides  con- 
tracted towards  the  bottom,  in  which  case  they  are  called  dove-tail 
rails.  These  ]}  rails  are  easily  manufactured,  far  more  so  than  the 
generally  employed  I  rail.  The  difficulty  of  filling  the  flanches 
is  not  so  great  as  in  the  latter  rail;  and  if  the  railroad  companies 


360  MANUFACTURE    OF  IRON. 

understood  their  own  interest,  we  doubt  not  that  they  would  much 
prefer  the  £)_  to  the  i  rail;  the  iron  works  also  would  find  the 
former  more  profitable.  In  making  j}  rails,  almost  any  kind  of 
iron,  even  the  strongest,  can  be  employed,  and  a  good  article  of 
course  manufactured.  But  for  the  cheap  manufacture  of  i  rails, 
the  iron  must  be  of  a  particular  quality.  The  weakest  iron  works 
generally  the  best.  Strong  and  very  good  iron  will  not  fill  the 
flanches,  even  though  it  is  made  hot  enough  to  work  well.  There- 
fore, it  follows  that  a  great  deal  of  weak  iron  is  used  in  making 
the  IE  rails,  which  would  not  be  employed  if  _Q  rails  were  in  as 
much  demand  by  the  railroad  companies.  If  there  is  a  special 
advantage  in  the  in  section,  we  are  ignorant  of  it.  We  know  that, 
if  the  jQ  section  were  employed  instead  of  it,  there  would  be  a  pros- 
pect of  having  better  material  in  the  rail.  There  is  but  little  diffi- 
culty in  manufacturing  a  bridge  rail,  and  as  the  principle  involved 
in  rolling  this  or  the  IE  rail  is  the  same,  we  will  describe  the  latter. 
b.  Rollers  for  shape  rails  ought  to  be  at  least  twenty-two  inches  in 
diameter,  and  make  from  sixty-five  to  seventy-five  revolutions  per 
minute.  This  diameter  is  required  on  account  of  the  deep  grooves 
in  the  roughing  as  well  as  finishing  rollers.  A  pile  for  a  rail  eight 
yards  in  length,  sixty-five  pounds  per  yard,  must  be  thirty-two  inches 
long  by  ten  or  eleven  inches  square;  a  large  groove  in  the  roughing 
rollers  is  thus  needed  to  catch  the  pile.  One  of  the  worst  of  specula- 
tions is  to  make  the  grooves  in  the  rough  rollers  too  narrow,  for  delay 
is  thus  occasioned.  Heavy  packs  are  too  porous  and  too  hard  to 
catch  the  rollers  easily,  if  the  grooves  are  too  narrow  to  make  the 
rollers  bite.  Cutting  the  grooves  or  throwing  on  sand  is  of  doubtful 
advantage,  for  this  occasions  a  loss  of  time  in  all  instances.  At 
least,  it  is  not  advisable  to  make  the  first  groove  too  narrow,  in  anti- 
cipation of  the  advantage  obtained  from  cutting  it.  The  rollers 
may  be  cut,  and  made  rough  in  any  way  we  choose ;  but  that  ought 
to  have  no  bearing  whatever  upon  their  size,  or  upon  that  of  the 
grooves.  The  loss  at  the  roughing  rollers,  caused  by  the  iron  get- 
ting too  cold,  is,  of  all  others,  the  most  disagreeable,  because  the 
iron  is  generally  too  long  to  be  re-heated,  and  too  thick  to  be  cut 
through  with  ease.  It  is  unnecessary  to  furnish  a  drawing  of  the 
roughing  rollers,  for  they  do  not  vary,  except  in  size,  from  those 
already  described.  We  annex,  however,  an  illustration  of  a  pair 
of  finishing  rollers  for  i  rails,  as  the  most  common.  The  form  of 
the  grooves  represented  here  may  be  considered  as  not  generally 
applicable.  Different  kinds  of  iron,  and  the  hardness  of  iron  and 


FORGING  AND   ROLLING.  361 

texture,  make  a  slight  difference  in  the  form  of  the  grooves  necr 
sary.     Fig.  118  shows  the  gradual  transformation  of  the  square 


Fig.  118. 


Grooves  for  I  rails. 

billet.  It  is  received  by  the  grooves  No.  1,  No.  2,  and  No.  3.  These 
work  out  both  flanches  to  a  certain  degree,  as  wide  in  the  base  as 
actually  necessary,  but  leaving  the  bottom  flanch  somewhat  thicker. 
No.  4  presses  the  bottom  and  top  smooth,  and  works  the  bottom 
flanch  down  to  its  proper  thickness,  and  somewhat  broader.  No.  5 
and  No.  6  are  almost  of  equal  form  and  size,  giving  the  finishing  touch 
to  the  rail.  The  decrement  of  the  grooves  is  very  limited,  and  there 
is  no  difficulty  whatever  in  making  a  straight  rail,  even  with  one 
groove  less.  The  first  groove  is  cut  entirely  in  the  bottom  roller, 
and  the  form  of  it  is  calculated  to  fill  the  bottom  flanches  of  the  rail 
with  sound  iron.  The  width  of  the  flanches  is  often  kept  smaller 
in  this  first  groove  than  it  is  to  be  when  finished ;  but  we  think 
this  a  wrong  proceeding,  and  only  admissible  with  weak  and  cold- 
short iron.  Strong,  tenacious  iron  will  not  fill  the  flanch,  if  once 
too  small,  or,  at  best,  it  will  make  but  broken  edges,  which  re- 
quire a  great  deal  of  patching.  The  proper  shape  of  No.  1  is  that 
in  which  the  bottom  of  the  rail  is  brought  to  such  a  size  as  to 
afford  sufficient  iron  to  the  grooves  Nos.  2  and  3  to  work  both 
flanches  equally  down.  For  doing  this,  a  greater  breadth  of  the 
groove  is  needed  than  the  rail  will  have  when  finished;  and  an  ex- 
cess in  this  direction  is,  in  no  instance,  disadvantageous.  If  the 
breadth  is  increased  in  this  first  groove,  the  thickness  may  be  dimin- 
ished, which  is  very  advantageous,  particularly  with  thin  flanches 
and  strong  iron.  The  reduction  of  a  square  billet  to  the  size  of  No. 
1  is  too  much  for  one  groove,  and  a  more  triangular  groove  may 
precede  that  size.  If  the  rollers  are  more  than  forty-two  inches 


362  MANUFACTURE   OF   IRON. 

long,  and  the  metal  in  the  rollers  good,  the  grooves  may  be  so 
arranged  as  to  admit  one  more  in  that  length.  If  they  are  short, 
or  if  the  casting  is  weak,  a  triangular  groove  may  be  cut  in  the 
rough  rollers,  where  room  can  generally  be  spared.  Groove  No.  1 
is  better  in  the  finishing  rolls,  for  it  bears  relation  to  the  final  form 
of  the  rail,  and  must  vary  in  shape  according  to  that  of  the  rail.  The 
grooves  Nos.  2  and  3  work  the  rail  very  nearly  to  its  ultimate  size  ; 
but  they  make  the  rail  somewhat  too  high.  This  surplus  height 
is  reduced  in  No.  4,  where  the  bottom  and  top  are  smoothed,  and 
the  bottom  flanches  reduced  to  the  proper  thickness,  making  the 
base  a  little  broader  than  the  final  measure  is  to  be.  Grooves 
Nos.  5  and  6  serve  merely  for  finishing ;  they  are  of  the  form  of 
the  rail  when  finished — No.  5  somewhat  larger  than  No.  6.  In 
these  grooves,  the  rail  receives  a  uniform  reduction  in  every  part, 
except  in  the  thickness  of  the  bottom  flanch,  and  in  the  height  of 
the  rail,  which  cannot  be  reduced. 

The  castings  for  this  kind  of  rollers  are  to  be  of  good  metal,  of 
strong,  but  not  very  gray  cast  iron.  Rollers  for  flat  iron  must  gene- 
rally be  good  castings,  on  account  of  the  flanches  or  collars ;  these 
are  mostly  high,  and  liable  to  be  affected  by  pressure  and  sudden 
change  of  temperature,  which  frequently  injure  a  roller  so  much  as 
to  make  it,  in  a  comparatively  short  time,  unfit  for  service.  The 
collars  on  rail  iron  rollers,  and  all  heavy  flat  iron,  must  be  strong, 
and  with  the  best  iron  not  less  than  two  inches  thick ;  this  thick- 
ness is  to  be  increased,  if  the  length  of  the  roller  will  admit  of  it. 

c.  The  heavy  packs  or  piles  of  railroad  iron  are,  in  many  estab- 
lishments of  England  and  Wales,  brought  from  the  first  heat  to  the 
T  hammer  for  welding.  This  practice  is  not  common  in  this 
country,  nor  anywhere  else  ;  it  is  necessary  where  iron  is  employed 
which  is  too  weak  to  bear  a  strong  heat.  A  heavy  pack  of  weak 
iron,  if  heated  to  a  welding  heat,  will  split  in  being  roughened  down. 
To  prevent  this,  such  piles  are  to  be  brought  to  the  hammer,  which 
will  give  the  iron  a  small  compression,  and  an  imperfect  welding, 
making  it  less  liable  to  open  in  the  rollers.  Well-worked  iron,  which 
will  bear  a  welding  heat,  is  not  very  liable  to  open  in  the  rollers, 
thus  saving  the  expenses  of  shingling.  Instead  then  of  shingling 
the  pile,  it  is  pushed  through  the  roughing  rollers  and  reduced  to  a 
six  or  seven  inch  billet,  which  is  returned  to  the  re-heating  furnace. 
This  is  a  very  advantageous  way  of  working,  in  case  the  iron  is  of 
good  quality.  The  carrying  of  heavy  piles  from  the  re-heating  furnace 
to  the  rollers  is  performed  by  means  of  iron  cars,  just  high  enough 


FORGING  AND  ROLLING.  363 

to  reach  the  furnace  door,  and  not  too  high  to  reach  the  rollers.  In 
case  the  rollers  will  not  bite,  this  car  is  made  use  of  to  strike  the 
end  of  the  pile,  and  force  it  into  them.  Such  a  car  must  he  very 
strong,  and  entirely  made  of  wrought  iron;  it  should  have  on 
the  top  a  series  of  friction  rollers,  two  inches  round;  these  re- 
ceive and  discharge  the  heavy  piles  more  easily  than  traverse  bind- 
ers. At  the  roughing  rollers,  two  workmen  before  and  two  behind 
are  needed,  one  on  each  side  using  the  tongs  and  the  other  catching 
with  a  suspended  hook,  close  to  the  tongs,  in  order  to  help,  or,  in 
fact,  to  carry  the  whole  weight  of  the  end  of  the  bar;  the  roller  and 
catcher,  before  and  behind  the  rollers,  using  their  tongs  merely  to 
turn  the  billet.  At  the  finishing  rollers,  there  should  be  at  least  two 
workmen  before,  and  three  behind  the  rollers;  and,  if  the  rails  are 
long  or  weak,  three  before  and  three  behind  having  each  a  hook, 
suspended  on  long  rods;  these  hooks  follow  the  rail  in  its  motion, 
and  support  it  against  bending  by  its  own  weight. 

After  a  rail  is  finished  in  the  rollers,  it  is  carried  to  the  saws,  to 
be  cut  square  at  the  ends.  These  are  circular  saws,  with  coarse 
teeth,  and  about  three  feet  in  diameter,  made  of  sheet  iron,  or, 
as  in  some  cases,  of  steel.  They  move  with  great  rapidity,  and 
cut  a  rail  through  in  a  few  seconds,  making  from  1200  to  1500 
revolutions  per  minute.  Fig.  119  represents  a  sawing  machine 

Fig.  119. 


Saw  machine  for  squaring  the  ends  of  railroad  and  heavy  bar  iron. 

for  cutting  off  the  ends  of  rails  and  other  heavy  iron.  There  are 
two  saws  moving  at  the  same  time,  and  kept  in  motion  by  the  straps 
a,  a.  The  distance  between  these  saws  is  to  be  somewhat  greater 
than  the  length  of  the  rail,  so  that  but  one  end  will  be  cut  at  a 
time,  after  which  the  rail  is  moved  longitudinally,  and  the  other 
end  cut  off.  Equal  lengths  in  rails  are  rarely  insisted  on  by  the 
railroad  companies,  and  almost  any  length  is  suitable  which  is 
within  given  limits.  With  good  iron,  and  by  proper  care,  the  sound- 


364  MANUFACTURE    OF  IRON. 

ness  of  the  bar  to  the  very  ends  will  be  secured ;  and  only  a  few 
inches  are  lost  in  squaring.  Ill- worked  iron  frequently  loses  from  one 
to  one  and  a  half  feet  at  each  end,  which  is  equal  to  from  twelve  to 
twenty  per  cent.  The  hot  rail  is  placed  and  moved  towards  the  saws 
on  an  iron  bench,  which  slides  in  the  parallel  prisms  <?,  <?,  c.  It  is  moved 
by  a  long  horizontal  shaft,  lying  between  the  saws.  On  this  shaft — 
which  is  turned  by  an  iron  handwheel  of  the  shape  of  a  light  fly- 
wheel— are  two  small  pinions,  one  on  each  end,  which  work  in 
corresponding  racks  d,  d,  fastened  to  the  bench,  and  moving  it  to 
and  from  the  saws.  The  cutting  of  a  heavy  bar  of  hot  iron  is  a 
beautiful  sight — -the  rapidly  moving  saw  throwing  off  a  profusion  of 
small  particles  of  iron,  which  burn,  in  darting  through  the  air,  with 
a  vivid  and  brilliant  light.  They  would  injure  the  workmen  engaged 
at  this  business,  if  the  saw  were  not  covered  by  a  protecting  screen. 
The  lower  part  of  the  saw  runs,  at  many  establishments,  in  cold 
water,  to  prevent  its  getting  hot,  in  consequence  of  the  heat  and 
rapid  motion. 

From  the  saws,  the  rail  is  put  upon  the  straightening-bench,  which 
is  a  long,  straight,  cast  iron  plate,  ten  or  twenty  inches  wide,  hav- 
ing on  one  edge  a  projecting  rib.  This  bench  is  used  for  com- 
mon flat  and  square  iron,  for  flat  rails,  and  rails  whose  top  and 
bottom  are  of  equal  size ;  but  for  bridge  rails  or  31  rails,  such 
a  bench  will  not  answer.  Any  iron,  or  rails,  the  one  part  of 
whose  section  is  composed  of  thinner  parts  than  the  other,  will  not 
remain  straight  after  it  has  been  straightened  when  warm.  The 
thin  parts  will  become  cold  sooner  than  the  thick  parts ;  this  pro- 
duces an  unequal  contraction,  and  gives  a  curvature  to  the  for- 
merly straight  bar.  A  _Q  or  x  rail  is  generally  broad  and  thin, 
in  its  lower  part  or  base,  in  proportion  to  its  top,  and,  conse- 
quently, if  straightened  on  a  straight  bench,  it  will  gradually 
assume  a  curvature  concave  at  the  top  of  the  rail.  To  prevent  this, 
convex  straightening  benches  are  employed,  whereupon  the  rail  is 
bent,  by  means  of  heavy  wooden  mallets,  into  a  convex  form,  which 
will  straighten  as  the  rail  gradually  cools  off.  The  convexity  of 
such  a  bench  depends  on  the  section  of  the  rail  and  the  quality  of 
the  iron ;  it  is  generally  from  an  inch  to  an  inch  and  a  half  to  every 
yard  of  the  rail.  As  the  rail  gradually  cools  off,  and  straightens 
itself,  it  is  removed  from  the  bench  to  large  platforms,  provided  with 
two  parallel  rails  distant  from  each  other  nearly  the  length  of  the 
rail,  along  which  the  rails  easily  move.  Three  or  four  such  platforms 


FORGING  AND  ROLLING.  365 

in  succession  are  required  under  one  shed;  their  form  must  be 
nearly  square — that  is  to  say,  their  extent,  lengthwise  and  cross- 
wise, should  be  equal  to  that  of  a  rail.  On  the  first  platform, 
the  rails  are  overhauled  by  means  of  coarse  files,  and  any  imper- 
fection or  unsoundness  of  iron  exposed.  Those  which  cannot  well 
be  improved  by  patching  are  removed.  Between  the  first  and 
second  platform  a  very  heavy  cast  iron  anvil  is  placed,  on  which 
the  final  straightening  of  the  rails  is  performed  ;  for  that  purpose, 
heavy  iron  sledges  weighing  from  twenty  to  thirty  pounds  are  used. 
Between  the  second  and  third,  fourth  and  fifth  scaffold,  the  rails 
are  patched.  This  consists  in  fitting  in  small  pieces  of  iron  into 
the  defective  parts.  In  the  rolling  of  IE  rails,  there  is  sometimes 
difficulty  in  bringing  out  their  flanches;  in  this  case,  we  succeed 
far  better  with  cold-short,  or  impure,  dirty  iron,  than  with  pure, 
strong,  and  fibrous  iron.  This  difficulty  increases  with  the  dimin- 
ished thickness  of  the  flanches,  and  cannot  be  avoided  if  the  iron 
is  very  strong,  or  free  from  cinder.  Weak  iron,  or  cold-short  iron 
can  be  worked  to  great  perfection,  if  the  pile  is  turned  in  such  a 
way  that  the  joints  of  the  mill  bars  fall  perpendicularly  upon  the 
bases  of  the  rail.  If  taken  in  the  opposite  direction,  even  the 
weakest  iron  will  not  make  full,  broad,  and  thin  flanches.  To  what 
extent  the  quality  of  a  rail  is  impaired,  in'  consequence  of  these 
practical  difficulties,  it  is  not  our  province  to  investigate.  But  we 
may  say  that  the  quality  of  rails  might,  in  most  cases,  be  made, 
from  the  same  materials,  far  superior  to  what  it  now  is.  If  the 
constructing  engineer  of  a  railroad  would  reflect  upon  the  best  prac- 
tical form  of  a  rail,  and  alter  its  section  accordingly,  there  is  no 
doubt  that  great  advantages  might  be  realized.  With  respect  to 
Q  rails,  or  rails  with  equally  thick  flanches,  the  above  difficulty 
does  not  exist,  at  least  not  to  so  great  an  extent.  The  making  of 
rails  may  be  considered  the  most  pleasant  and  easy  branch  in  the 
whole  extent  of  the  iron  manufacturing  business. 

VI.  Sheet  Iron. 

The  making  of  sheet  iron  is  a  branch  full  of  intricacies  and 
difficulties ;  but  once  thoroughly  understood,  it  is  very  simple  and 
agreeable.  The  main  difficulty  we  encounter  depends  upon  the  qua- 
lity of  iron  from  which  it  is  made.  Charcoal  iron  generally  works 
well ;  but  some  kinds  of  puddled  iron  do  not  make  good  sheet  iron. 
We  alluded  to  this  in  our  remarks  on  puddling,  but  propose  to 
speak  of  it  again  at  the  close  of  this  chapter.  Sheet  iron  was 


366  MANUFACTURE    OF   IRON. 

made  in  ancient  times  by  means  of  forge  hammers  ;  it  was  flattened 
down  by  broad-faced  hammers  on  large  anvils.  This  method  is 
still  practiced  in  the  eastern  parts  of  Europe.  At  the  present  day, 
and  in  our  own  country,  sheet  iron  is  rolled.  It  is  made  partly 
from  charcoal  blooms,  and  in  some  places  from  puddled  iron. 

a.  In  all  cases  where  thin  sheet  iron  is  to  be  made,  the  iron  must 
first  be  converted  into  flat  mill  bars.     Charcoal  blooms,  as  well  as 
puddled  iron,  undergo  the  same  treatment,  with  this  difference,  how- 
ever, that  good  charcoal  blooms  do  not  require  a  welding  heat. 
Puddled  iron  is  to  be  piled,  and  a  pack  of  rough  bars  welded  and 
rolled  down  into  flat  mill  bars.     These  bars  are  from  four  to  six 
inches  wide,  varying  in  thickness,  according  to  the  number  of  sheets 
to  be  made  from  them.     Heavy  sheet  iron  and  boiler-plate  are  to 
be  made  from  mill  bars,  if  we  want  a  good  article.     Sheet  iron  is 
principally  made  from  charcoal  blooms  shingled  down  into  slabs ; 
sometimes  from  puddled  rough  bars,  piled,  welded,  and  shingled 
by  the  T  hammer  into  slabs.     By  neither  method  is  good  boiler- 
plate made ;  a  second  re-heating  is,  in  all  cases,  to  be  resorted  to, 
if  we  want  the  best  article  the  material  is  capable  of  producing. 
In  the  manufacture  of  sheet  iron,  our  main  attention  must  be  con- 
centrated upon  the  quality  of  the  iron,  and  the  power  at  our  ser- 
vice.    All  other  matters  are  of  subordinate  importance,  and  have 
little  bearing  upon  the  success  of  our  operations.     Clean,  white, 
fibrous  iron,  and  a  surplus  of  power,  are  the  most  essential  elements 
in  making  good  and  cheap  sheet  iron. 

b.  The  machinery  for  making  sheet  iron  does  not  materially  vary, 
except  as  regards  strength,  from  that  used  in  making  bar  iron.    The 
housings  are  generally  heavier,  in  Europe  often  made  of  wrought 
iron;  the  junction  shafts  and  coupling  boxes  stronger;  the  fly- 
wheels heavier.    The  length  of  the  rollers  is,  in  most  cases,  but  three 
feet  between  the  gudgeons ;  seldom  three  and  a  half  feet  for  thin 
sheet.    For  the  rolling  of  boiler-plate,  we  find  rollers  four  and  even 
five  feet  long  in  use.    The  diameter  varies  according  to  the  length. 
A  short  roller  may  be  of  smaller  diameter  than  a  long  one ;  and 
weak  cast  iron,  of  course,  will  make  a  larger  diameter  necessary 
than  strong  castings.     In  Fig.  120,  a  set  of  sheet  rollers  is  repre- 
sented.    The  pinions  and  pinion  standards  are  not  generally  em- 
ployed; they  are  unnecessary,  and  even  disadvantageous,  for  making 
thin  sheet.     But  for  roughing  down,  when  the  plates  are  thick,  or 
for  making  boiler-plate,  they  are  advantageous,  and  save  a  great  deal 
of  breakage.    Slabs  which  are  one  and  a  half,  or  two  or  more  inches 


FORGING   AND   ROLLING.  367 

thick,  lift  the  top  roller  very  high,  and  suddenly  drop  it ;  th'^>;  of 
course,  produces  a  heavy  shock  all  through  the  machinery.  To 
avoid  this  shock,  the  top  ought  not  to  touch  the  bottom  roller:  ln.it 

Fig.  120. 


Rollers  and  pinions  for  sheet  iron. 

then  the  pinions  are  necessary;  without  them  the  top  roller  will  not 
move,  and  unless  this  moves,  the  rollers  will  not  bite.  In  cases  where 
the  top  moves  independently  of  the  bottom  roller,  the  first  is  gene- 
rally balanced  by  counter  weights,  applied  either  below  or  above 
the  rollers;  these  weights  keep  the  top  and  bottom  rollers  apart. 
We  think  that  the  arrangement  indicated  in  Fig.  109,  for  keeping 
the  top  roller  up,  is  far  preferable  to  any  other.  The  wrenches  on 
the  top  screws  form  a  cross,  so  as  at  any  time  to  expose  a  handle 
to  the  workmen  before  the  rollers.  The  distance  between  the 
rollers  must  be  perfectly  controlled  by  the  foreman,  because  he 
regulates  the  thickness  of  the  sheet  by  these  screws.  Of  all  the 
improvements  made  relative  to  the  regulation  of  the  distance  be- 
tween the  rollers,  none  is  preferable  to  the  above  simple  mode. 

c.  For  making  very  thin  and  polished  sheet  iron,  cast  iron  hous- 
ings are  not  sufficiently  strong,  unless  very  heavy,  and  of  the  best 
kind  of  iron.  In  this  case,  wrought  iron  standards  are  prefer- 
able; and,  as  there  is  no  difficulty  in  obtaining  heavy  and  good 
wrought  iron,  at  reasonable  prices,  in  Eastern  Pennsylvania,  where 
it  is  manufactured  up  to  seven  inches  in  diameter,  it  may,  in 
many  instances,  be  advantageous  to  employ  such  standards.  In 


368  MANUFACTURE   OF  IRON. 

Fig.  121,  a,  a  represent  wrought  iron  pillars;  these  are  fastened 
by  being  cast  into  the  bottom-plate.      Each  of  these  pillars  is 


Fig.  121. 


provided  with  a  screw  and  nut ;  the  advantage  of  taking  small,  very 
minute  grades  of  pressure,  decrement,  upon  the  top  roller  is  thus 
secured.  For  the  making  of  thin  sheet  iron,  this  is  a  very  con- 
venient and  essential  arrangement.  The  aprons  are  broader  than 
at  bar  iron  rollers,  which  is  indispensable.  If  heavy  plates  are  to 
be  rolled,  even  small  friction  rollers  in  the  apron  are  to  be  added 
on  the  work  side.  The  friction  of  heavy  iron  upon  the  apron  is 
great,  and  the  employment  of  additional  hands  would  be  necessary, 
if  this  friction  were  not  diminished  by  the  above  friction  roller. 
Sheet  rollers  move  with  various  speed,  and  the  foreman  ought  to 
have  it  in  his  power  to  give  to  them  just  the  degree  of  speed  re- 
quired. The  speed  necessary  for  these  rollers  is  from  twenty  to 
forty  revolutions.  In  a  well-conducted  establishment,  there  are 
roughing-rollers,  finishing  rollers,  and  hard  or  chilled  rollers.  We 
generally  find  only  the  two  first,  and  in  very  few  establishments 
the  last. 

d.  For  making  boiler-plate,  but  one  pair  of  rollers  is  needed,  and 
the  slab  rolled  down  in  one  heat.    The  slab,  as  received  from  the  T 


FORGING   AND   ROLLING.  369 

hammer,  is  generally  from  twelve  to  eighteen  inches  long,  from 
seven  to  ten  inches  wide,  and  from  two  to  three  inches  thick.  It  is 
heated,  in  a  re-heating  furnace,  to  a  bright  red,  but  not  welding 
heat.  The  dimensions  of  the  sheet  to  be  rolled  from  a  given  slab 
are  produced  by  turning  the  slab  more  or  less,  and  increasing  in 
one  direction.  The  surface  of  the  iron  is  repeatedly  chilled  by 
sprinkling  cold  water  on  it  by  means  of  a  broom;  this  loosens  the 
adhering  scales,  which  may  then  be  removed  by  turning  the  plate, 
or  by  the  broom.  This  operation  must  be  particularly  attended  to 
when  the  plate  is  nearly  finished.  Polish  and  great  smoothness  are 
not  required  for  boiler-plate.  Uniform  thickness  and  good  quality 
of  iron  are  the  main  requisites. 

e.  Sheet  iron  thinner  than  boiler-plate  is  generally  rolled  from 
platines,  or  from  cuttings  of  flat  merchant  bars.  That  which  is 
heavier  may  be  made  from  one  length  of  the  flat  mill  bar ;  and  two, 
or  even  three  thicknesses,  when  sufficiently  heated,  are  welded  to- 
gether in  the  sheet  rollers.  Common  sheet  iron,  as  No.  15  and 
higher  numbers,  is  made  from  one  thickness  of  the  mill  bars,  whichr 
heated  to  a  cherry-red  heat,  is  run  through  the  rollers  in  single 
sheets.  At  subsequent  heats,  two,  or  even  three  may  be  rolled 
together.  When  heated,  the  mill  bars  or  platines  are  brought  from 
the  oven  in  pairs, which  are  pushed  singly  through  the  rollers.  This 
keeps  the  workmen  actively  employed;  for,  while  one  plate  is  be- 
tween the  rollers,  the  other  is  returned  over  the  top  roller,  the  one 
thus  closely  following  the  other.  If  three  plates  are  at  once  in 
motion,  still  more  active  manipulation  is  required,  for,  while  one 
plate  is  between  the  rollers,  the  two  other  plates  are  in  the  tongs  on 
each  side  of  them.  In  the  first  heat,  the  iron  is  reduced  as  much 
as  possible;  and  to  what  extent  it  may  be  brought  to  the  desired 
form,  depends  on  the  power  of  the  engine,  and  the  dexterity  of  the 
workmen.  In  this  heat,  the  breadth  of  the  sheet  is  determined,  in 
case  the  platines  are  not  already  cut  to  the  proper  length. 

After  this  operation,  the  iron,  which  already  assumes  the  appear- 
ance of  sheet  iron,  is  returned  to  the  heating  oven,  or,  as  in  well- 
conducted  establishments,  it  is  heated  anew  in  a  more  advantageous 
oven.  From  this  second  heat,  two  sheets  are  taken  and  rolled 
together,  with  the  caution  that,  after  passing  them  two  or  three 
times  through  the  rollers,  they  are  separated,  and  their  sides  re- 
versed, partly  to  prevent  the  adhesion  of  the  plates,  and  partly  to 
impart  a  smooth  surface  to  both  sides  of  the  sheets.  Sheet  iron  for 
24 


370  MANUFACTURE    OF  IRON. 

the  manufacture  of  nails,  and  other  common  purposes,  is  in  this 
heat  generally  finished;  but  a  deficiency  of  power,  or  want  of  skill 
on  the  part  of  the  workmen,  frequently  makes  it  necessary  to  give 
it  an  additional  heat. 

Sheet  iron  of  less  thickness  and  of  higher  polish,  such  as  that 
used  for  stove  pipes,  requires  another  heat,  and  sometimes  several 
additional  heats.  An  ordinary,  smooth  surface  will  be  produced  by 
passing  sheets,  two  by  two,  through  rollers  of  tolerable  hardness. 
But  if,  in  this  heat,  the  sheets  are  passed  singly  through  the  rollers, 
before  which  a  scraper  is  put  to  clean  the  surface  from  the  coarsest 
part  of  the  adhering  scales,  a  finer  surface  is  produced.  For  this 
purpose,  common  rollers  of  good  close  castings  are  sufficient.  But 
if  a  still  finer  surface  is  required,  hard  and  highly  polished  rollers 
are  necessary.  To  such  thin  sheet  iron  a  high  degree  of  power 
must  be  applied,  because  the  iron,  when  passing  through  the  roll- 
ers, is  very  nearly  cold.  For  this  reason  the  rollers  are  made  only 
from  twenty-two  to  twenty-four  inches  in  length,  while  their  diame- 
ter is  sixteen  or  eighteen  inches ;  the  housings  of  great  strength,  and 
the  power  applied  greater  than  in  any  other  case.  Highly  polished 
sheet  iron  of  larger  size  than  twenty  inches  in  width,  and  four  or 
five  feet  in  length,  is  seldom  made. 

In  making  sheet  iron,  it  is  sometimes  difficult  to  obtain  the  pre- 
cise color  which  the  manufacturer  desires.  Such  a  color  is  a  bright, 
light  blue,  or  that  of  Russian  sheet  iron.  Experience  proves  that 
from  impure  iron  we  cannot  obtain  a  bright,  silvery-looking  sur- 
face. But  the  color  of  the  best  and  purest  iron  may  be  destroyed 
by  the  influence  of  the  fuel,  To  give  a  bright  surface  to  sheet 
iron,  we  require,  in  addition  to  hard  and  well-polished  rollers,  the 
removal  of  the  scales,  as  far  as  possible,  from  the  surface  of  the 
white  or  pure  iron,  which  ought  to  shine  through  the  thin  coating 
of  magnetic  oxide.  The  brightest  colors  are  received  from  the 
whitest  iron.  It  is  thus  seen  that  the  color  has  no  relation  to  the 
purity  of  the  metal.  We  have  seen  very  beautiful  sheet  iron  made 
from  very  cold-short  iron  containing  phosphorus,  and  very  cloudy- 
looking  black  sheets  from  the  best  and  toughest  charcoal  iron.  If 
we  wish  to  make  a  light,  fine-looking  sheet  iron,  a  portion  of  carbon, 
or  even  of  phosphorus  and  silicon,  will  be  advantageous.  In  very 
thin  sheets,  the  most  cold-short  iron  is  malleable;  and,  therefore,  in 
this  instance,  it  is  useful.  White  iron — whether  the  whiteness  arises 
from  impurities,  or  from  remarkable  purity — separates  easily  from  its 
scales,  and  is  on  that  account  preferable  to  metal  of  any  other  color. 


FORGING  AND  ROLLING.  371 

/.  The  color  of  sheet  iron  is  affected  not  only  by  the  quality  of 
the  iron,  but  also  by  fuel,  and  by  the  construction  of  the  heating 
ovens.  Sulphur  imparts  a  black  color  to  iron,  if  present  only  in 
very  minute  quantity;  and  it  may  be  regarded  as  an  impossibility 
to  make  a  fine-looking  sheet  iron  in  cases  in  which  sulphurous  coal 
is  employed.  Though  the  iron,  in  such  cases,  may  be  of  the  best 
quality,  the  sheets  will  appear  of  a  cloudy,  black,  or  of  a  dirty, 
dark  blue  color.  Pure  carbon  will  not  injure  the  color;  but  when 
present  in  connection  with  sulphur,  the  color  of  the  iron  will  be  en- 
tirely spoiled.  Therefore,  if  the  sheets  are  well  cleaned  in  the  third 
heat,  all  our  attention  should  be  concentrated  upon  the  endeavor  to 
protect  them  against  the  influence  of  sulphur,  pure  air,  and  against 
the  silicious  dust  which  is  thrown  out  by  anthracite  coal.  This 
can  be  effected  by  high  arched  ovens,  which  will  prevent  the  flame 
from  playing  on  the  iron.  We  should  select  fuel  free  from  sulphur ; 
and,  if  we  employ  anthracite,  we  should  secure  so  weak  a  draft  in 
the  oven  that  no  silicious  dust  shall  be  carried  over  from  the  grate 
to  the  furnace.  Charcoal  is  the  best  fuel.  In  fine,  by  employing 
charcoal,  clean  iron,  a  high  oven,  well-polished  rollers,  and  a  suffi- 
ciently strong  power,  we  shall  experience  no  difficulty  in  making 
the  finest  kind  of  sheet  iron.  Cleaning  the  iron  by  means  of  acids 
is  a  waste  of  time,  and  an  unnecessary  expense.  It  may  be  cleaned 
by  means  of  a  scraper,  on  the  principle  applicable  to  the  cleaning 
of  hoops,  without  difficulty. 

VII.  Re-heating  Furnaces. 

Re-heating  furnaces  are  those  which  serve  to  give  a  welding  heat 
to  the  iron.  In  these  furnaces,  either  piles  of  flat  rough  bars,  or 
single  billets  are  heated,  scraps  are  welded,  and  the  first  heat  to 
sheet  iron  is  given.  A  re-heating  differs  but  little  from  a  puddling 
furnace.  The  same  kind  of  chimney,  with  the  same  dimensions,  is 
employed,  and  the  outward  form  of  the  furnace  is  the  same  as  that 
of  the  puddling  apparatus.  Fig.  122  exhibits  a  re-heating  furnace, 
with  the  exception  of  the  chimney,  which  it  is  not  necessary  to  re- 
present. The  whole  interior,  with  the  exception  of  the  hearth  a,  is 
made  of  fire  brick.  The  hearth  is  constructed  of  sand.  For  this  pur- 
pose, a  purely  silicious  sand  is  required;  the  coarser  the  better. 
Pebbles  of  about  half  an  inch  in  size  are  the  very  best  article  we 
can  select.  If  no  sand  of  sufficiently  good  quality  can  be  conve- 
niently obtained,  white  river-pebbles,  or  white  sandstones,  burnt 
and  pounded  into  a  coarse  sand,  will  answer  for  making  the  bottom 


372  MANUFACTURE    OF  IRON. 

of  the  hearth.     The  hearth  slopes  very  much  towards  the  flue ; 
and  this  inclination  tends  to  keep  it   dry  and  hard.     Provided 

Fig.  122. 


Section  of  a  re-heating  furnace. 

the  sand  is  not  carried  off  by  the  flowing  cinder,  the  slope  can- 
not be  excessive.  The  iron  wasted  in  re-heating  is  combined  with 
the  silex  of  the  hearth,  and  forms  a  very  fusible  cinder,  which  flows 
off  through  the  opening  5,  at  which  there  is  a  small  fire  to  keep  the 
cinder  liquid.  The  sand  bottom,  from  six  to  twelve  inches  thick, 
rests  on  fire  brick.  After  two  or  three  heats,  it  is  generally  injured 
by  the  melting  cinder,  when  some  additional  sand  is  required  to 
fill  up  the  cavities  that  are  made.  The  height  of  the  fire  brick 
arch,  or  its  distance  from  the  sand  bottom,  is  seldom  more  than 
twelve  inches ;  and,  for  common  purposes,  it  can  be  reduced  to 
eight  inches,  without  injurious  results. 

a.  In  these  furnaces,  the  grate  is  very  large  in  proportion  to  the 
size  of  the  hearth  ;  and,  with  respect  to  the  rules  laid  down  for  the 
construction  of  puddling  furnaces,  extremely  large.  The  grate 
is  frequently  as  large  as  the  hearth,  and  seldom  of  less  size  than 
half  its  area.  The  mean  for  general  practical  application  lies  be- 
tween these  dimensions.  Nevertheless,  we  should  be  guided  by 
local  circumstances,  for  a  size  that  would  be  appropriate  in  one  case 
would  not  be  suitable  in  another.  The  rules  which  govern  us 
in  proportioning  the  size  of  the  grate  and  hearth  depend,  as  in  the 
case  of  the  puddling  furnace,  upon  the  quality  of  fuel  we  employ. 
That  is  to  say,  a  larger  grate  is  required  for  anthracite  than  for  bitu- 
minous coal,  and  a  larger  one  for  the  latter  than  for  wood.  We 


FORGING   AND  ROLLING.  373 

should  also  be  influenced  by  considerations  of  economy.  A  large 
grate  produces  a  greater  yield  than  a  small  one,  provided  the  roll- 
ers take  the  iron  fast.  A  large  grate  works  faster  than  a  small 
one,  and  consumes  less  fuel.  Hence,  the  advantages  appear 
to  be  in  favor  of  the  former.  But,  in  cases  of  slow  work,  and 
iron  of  small  dimensions,  the  reverse  is  the  fact.  The  hearth  of  a 
re-heating  furnace  ought  never  to  be  longer  than  five  feet,  and  it 
may,  with  advantage,  be  reduced  to  three  or  three  and  a  half  feet. 
A  long  hearth  will  produce  but  an  imperfect  welding  heat ;  it  works 
too  cold  either  at  the  bridge  or  at  the  flue.  The  flue  should  be  as 
wide  as  the  hearth,  and  contract  gradually  towards  the  chimney. 
This  produces  a  uniform  heat  throughout  the  hearth.  Where  a 
hearth  is  to  be  made  larger  for  special  purposes,  such  as  for  heat- 
ing rail  piles,  or  any  other  heavy  piles,  it  is  more  advantageous  to 
extend  its  breadth  than  its  length.  The  width  of  the  furnace  is 
generally  five  feet,  but  these  dimensions  may  be  extended  to  eight 
and  even  more  feet,  without  inconvenience. 

b.  The  quantity  of  iron  re-heated  in  a  good  furnace  depends  on 
circumstances.  Much  depends  on  the  character  of  the  mill,  and 
upon  the  kind  of  iron  we  design  to  produce.  A  good  furnace  will 
produce,  in  twenty-four  hours,  from  eight  to  ten  tons  of  iron  em- 
ployed for  coarse  bars  arid  hoops,  and  an  equal  amount  of  railroad 
and  other  heavy  iron.  But  it  will  not  produce  more  than  from  two 
to  four  tons  of  iron  designed  for  small  rods,  hoops,  and  wire. 
Where  small  iron  requiring  no  welding  heat  is  made  from  mill  bars, 
large  furnaces  may  be  employed.  By  this  means,  we  may  obtain 
twice  the  amount  just  stated,  if  such  an  extension  is  deemed  ad- 
vantageous. By  so  managing  the  furnace  as  to  make  a  heat  in 
the  shortest  possible  time,  we  shall,  in  all  instances,  arrive  at  the 
most  favorable  results.  The  time  required  will,  of  course,  vary 
according  to  the  size  of  the  iron.  Still,  it  is  evident  that  both  iron 
and  fuel  will  be  economized  in  proportion  to  the  shortness  of  the 
time  consumed  in  welding  a  given  amount  of  iron.  Another  good 
rule  is,  to  work  slowly  from  the  commencement  of  each  heat,  to 
charge  the  exact  amount  of  fuel  required  to  finish  a  heat,  to  keep 
the  temperature  as  long  as  possible  below  a  welding  heat,  and  then, 
after  suddenly  raising  the  temperature  to  that  standard,  to  draw 
as  fast  as  the  rollers  will  receive  the  iron.  Small  charges  of  iron 
generally  produce  a  better  yield  than  large  charges,  but  consume 
more  fuel.  Where  fuel  is  cheap,  and  iron  expensive,  it  is  better 


374  MANUFACTURE   OF  IRON. 

to  charge  only  a  small  amount  of  iron  at  a  time,  and  to  make  a 
proportionate  increase  in  the  number  of  heats. 

c.  Re-heating  furnaces  are  employed  for  welding  wrought  iron 
scraps.  For  this  purpose,  a  variation  in  the  height  of  the  arch  from 
the  bottom  of  the  furnace,  and  in  the  form  of  the  hearth,  is  required. 
The  height  of  the  arch,  in  such  cases,  is  generally  from  eighteen 
to  twenty  inches ;  and  the  hearth  is  somewhat  more  level  than 
usual.  In  some  establishments,  scraps  are  assorted,  and  put  up  in 
bundles  of  from  forty  to  fifty  pounds  each.  Due  care  is  taken  to 
have  the  pieces  of  iron  in  each  bundle  of  equal  size ;  that  is,  sheet  iron 
and  bar  iron  scraps  should  not  be  bound  up  together.  These  bundles, 
well  secured  by  binders,  after  receiving  a  welding  heat,  are  either 
shingled  or  rolled.  This  course  is  also  pursued  at  charcoal  forge 
fires.  At  these  fires  the  bundles  are  re-heated  singly,  and  drawn 
out  into  bar  iron,  according  to  the  method  commonly  practiced. 
At  some  places,  another  method  is  pursued.  This  consists  in 
charging  the  re-heating  furnace  with  loose  scraps,  applying  to  them 
a  welding  heat,  and  forming  balls  in  the  same  manner  that  they 
are  formed  in  the  puddling  furnace.  These  balls  are  brought  to 
the  T  hammer,  or  squeezer,  formed  into  blooms,  and  roughened 
down  into  bars,  as  puddled  iron.  Scraps  make  a  very  fine  bar 
iron,  particularly  in  the  charcoal  fire,  and  such  iron  is  highly 
valued  by  the  blacksmith.  Where  good  iron  is  generally  manufac- 
tured, there  is  no  special  demand  for  scrap  iron  rods.  Iron  made 
from  these  scraps  cannot  be  cheap ;  therefore,  there  is  no  advan- 
tage in  seeking  to  make  specific  qualities  of  it.  Where  scraps 
can  be  bought  at  reasonable  prices,  the  most  profitable  way  of 
using  them  is  to  cut  them  into  small  pieces,  about  the  size  of  one's 
hand,  and  to  charge  the  puddling  furnace  with  them.  This  should 
be  done  at  the  time  the  iron  in  the  furnace  is  so  far  worked  as  to 
be  nearly  ready  for  balling.  From  fifty  to  seventy-five  pounds 
may  be  thrown  in  at  one  time.  By  this  application,  the  puddled 
iron,  instead  of  being  injured,  will  be  benefited.  Thus,  large 
quantities  of  scraps  may  be  worked  to  advantage.  Wages  at  the 
puddling  furnace  are  not  only  economized,  but  the  excessive  waste 
of  iron  in  the  re-heating  furnace  and  the  forge  fire  is  obviated.  The 
cinder  of  the  puddling  furnace  protects  the  scrap  iron. 

VIII.  Heating  Ovens. 

Iron  which  is  sufficiently  soft  and  malleable  to  be  wrought  into 
any  shape  by  the  hammer  or  roller  does  not  require  a  welding  heat. 


FORGING   AND  ROLLING.  375 

For  such  iron,  a  cherry-red  heat  will  suffice.  This  heat  is  produced 
by  ovens  or  stoves.  In  these  ovens,  all  sheet  iron,  and  rods  which 
require  an  extra  polish,  or  tempering,  are  heated.  Charcoal  billets, 
from  the  forge,  are  also  heated  in  them,  to  be  rolled  into  rod  iron 
of  small  size. 

a.  These  ovens  may  be  heated  by  a  variety  of  methods,  and  with 
almost  any  kind  of  fuel ;  still,  every  caution  is  requisite  to  prevent, 
as  far  as  possible,  the  access  of  free  oxygen  and  steam,  for  both 
steam  and  oxygen  occasion  waste  of  iron.     For  these  reasons,  our 
statement  must  be  received  with  some  qualification.     Wood,  turf, 
and  brown  coal  are,  so  far  as  their  capacity  for  generating  heat  is 
concerned,  an  excellent  fuel;  but,  unless  they  are  very  dry,  the 
steam  generated  from  their  hygroscopic  water  will  oxidize,  and  thus 
destroy  an  amount  of  iron  whose  expense  will  not  be  counter- 
balanced by  the  entire  profits  derived  from  the  fuel  employed. 
Therefore,  instead  of  using  the  raw  material,  it  will  be  found  ad- 
vantageous to  use  only  the  charcoal  derived  from  charring  it. 

The  same  objections  which  apply  against  any  fuel  containing 
water — which  of  course  excludes  the  use  of  all  kinds  of  heating, 
re-heating,  and  puddling  furnaces — apply  against  waste  flame,  for 
this  contains  a  large  amount  of  steam,  or  free  oxygen. 

b.  The  ancient  form  of  a  heating  oven  was  that  of  a  common 
bake  oven,  with  this  difference,  that  the  bottom  was  formed  of  iron 
bars.    Upon  these  bars,  placed  in  the  form  of  a  grate,  coal  from  ten 
to  fifteen  inches  in  depth  was  laid.     The  iron  was  placed  upon  the 
coal,  after  the  oven  was  heated.  In  some  establishments,  such  ovens 
are  still  employed.     It  is  evident  that  a  portion  of  the  iron  in  con- 
tact with  the  fuel — particularly  raw  fuel,  such  as  turf,  brown  coal, 
and  bituminous  and  anthracite  coal — must  be  wasted.     The  only 
instance  in  which  such  an  arrangement  may  be  considered  profita- 
ble is  where  wood  charcoal  is  employed.     Even  the  best  coke  or 
turf  coal  is  not  sufficiently  pure  to  guarantee  success.     Stone  coal, 
coke,  and  turf  are  never  free  from  sulphur,  and  this  sulphur  will  of 
course  combine  with  the  iron.     A  waste  of  iron  is  thus  occasioned 
exactly  proportionate  to  the  amount  of  sulphur  the  fuel  contains. 
In  addition  to  this,  sulphur  blackens  the  metal,  which,  in  the  case 
of  sheet, iron  and  nail  plates,  gives  rise  to  very  disagreeable  conse- 
quences.    Fuel  burned  in  this  way,  even  though  spread  in  a  high 
column  upon  the  grate,  never  combines  with  all  the  oxygen  which 
passes  through  the  coal;  the  result  is  a  waste  of  iron.     Therefore, 
there  is  every  reason  why  such  ovens  are  not  serviceable. 


376 


MANUFACTURE   OF   IRON. 


c.  Heating  ovens  of  a  superior  kind  are  at  present  constructed  on 
the  principle  of  the  reverberatory  furnace.  In  these,  the  fuel  and 
iron  are  properly  separated,  and  all  contact  between  them  obviated. 
Fig.  123  represents  a  vertical  section  of  a  heating  oven  for  sheet 

Fig.  123. 


Heating  oven  for  sheet  iron. 

iron;  a  is  the  hearth,  b  the  fire  grate,  and  c  the  chimney.  The 
height  of  the  furnace  is  often  thirty  inches.  The  object  of  this  is 
partly  to  prevent  the  contact  of  the  flame  and  iron,  but  principally 
to  gain  room  for  setting  the  sheet  edgewise;  they  are  thus  set  on 
both  sides  of  the  furnace;  besides,  in  the  middle  of  the  hearth, 
sufficient  room  is  left  for  laying  a  sheet  or  two  flatwise,  c?  is  a  cast 
iron  plate,  forming  a  sliding  door.  The  chimney  has  two  flues,  the 
one  inside,  the  other  outside  of  the  oven.  Its  draft  is  weak,  and  the 
smoke  or  flame  frequently  issues  from  the  mouth,  in  which  case  it 
is  carried  off  by  the  second  or  outside  flue.  Fig.  124  represents  a 
vertical  section  across  the  furnace  and  the  flues ;  and  Fig.  125  a 
ground-plan  of  the  furnace,  hearth,  and  fire-place.  The  cast  iron 
plate  e  is  here  shown  more  distinctly.  Its  object  is  to  protect  the 
bricks  or  stones  from  the  destructive  agency  of  the  tongs  and  iron. 
Like  puddling  and  re-heating  furnaces,  these  ovens  are  built  of 
fire  bricks,  enclosed  with  cast  iron  plates,  and  ^preserved  from  the 
effects  of  expansion  and  contraction  by  wrought  iron  cross  binders. 
A  slight  variation  from  the  form  of  the  oven  we  have  described, 
occasioned  as  well  by  individual  taste  as  by  locality,  is  sometimes 


FORGING   AND  ROLLING.  377 

observed;  still,  the  one  we  have  presented  is  the  one  generally 

Fig.  124. 


Front  elevation  of  a  heating  oven. 

employed  for  the  manufacture  of  sheet  iron.    If  it  is  desirable  that 
the  surface  of  the  iron  should  be  kept  very  clean,  the  fire  bridge 


Ground-plan  of  a  heating  oven. 

and  the  inside  flue  may  be  raised ;  but,  in  all  such  cases,  pure  fuel 
is  our  safest  reliance. 


378  MANUFACTURE   OF   IRON. 

IX.  Shears,  and  Turning  Machines. 

These  are  of  much  importance  in  a  rolling  mill.  The  first  we 
shall  describe  somewhat  minutely;  but  a  brief  description  of  the 
latter  must  suffice. 

a.  When  rollers  are  cast,  and  ready  for  turning,  they  are  placed 
upon  a  strong  and  heavy  turning  lathe,  and  the  gudgeons  and 
couplings  turned  between  points.     They  are  then  put  into  cast  iron 
standards,  into  which  brass  pans  are  inserted.     In  the  latter,  the 
gudgeons  revolve.     At  first,  the  rollers  are  turned  into  smooth 
cylinders.     After  a  set  is  thus  far  completed,  the  grooves  are  cut 
in,  according  to  a  design  previously  drawn  on  a  board.    Sheet  iron 
or  sheet  brass  patterns  are  made  for  each  groove  in  every  roller. 
These  should  be  preserved,  in  case  a  roller  is  injured,  or  fails  to 
answer  its  purpose.     Rollers  for  sheet  iron  are  of  course  smooth 
cylinders,  but  it  is  not  necessary  that  the  bottom  and  top  of  the 
roller  should  be  of  the  same  diameter.     Those  for  thin  sheet  iron 
should  be  turned  one  upon  the  other,  that  their  surfaces  may  be 
perfectly  parallel.    Unless  there  is  too  great  a  variation  in  the  sur- 
faces, this  may  be  done  in  the  housings.    After  using  the  rollers  for 
a  time,  their  surface  is  apt  to  become  rough.     Its  smoothness  may 
be  restored  by  cutting  it  with  one  edge  of  a  square  piece  of  cast 
steel,  from  three  to  four  inches  in  length.     This  operation  is  gene- 
rally performed  in  the  housings,  for  the  moving  of  the  rollers  to  the 
turning  lathe  is  attended  with  great  expense.    Good  hard  rollers  are 
turned  with  difficulty  by  common  methods.     A  steady  turning  ma- 
chine, of  slow  motion,  excellent  cast  steel  chisels,  and  patience,  are 
the  conditions  of  success.   Hard  rollers  are  required  for  making  thin 
and  polished  sheet  iron.    They  are  polished  by  means  of  emery  and 
leaden  pans,  which  extend  almost  quite  around  the  roller. 

b.  The  shears  required  in  a  mill  are  the  movable  hand-shears, 
for  cutting  small  rod  and  hoop  iron,  and  force-shears  connected  with 
a  waterwheel  or  steam-engine,  for  cutting  common  bar,  rough  bar, 
and  sheet  iron.     The  first  are  small  lever  shears,  fastened  upon  a 
two  inch  plank,  as  represented  in  Fig.  126.     The  length  of  the 
whole  is  about  two  feet  or  thirty  inches.     The  shears  are  placed  at 
each  end  of  a  pile  where  small  bar  or  hoops  are  deposited.     The 
boys,  who  catch  behind  the  rollers,  cut  off  the  bad  ends,  before  a 
rod  or  hoop  is  laid  down. 

c.  Fig.  127  represents  the  common  force-shear.     It  is  a  power- 
ful cast  iron  lever,  varying,  according  to  locality  and  purpose,  from 


FORGING  AND   ROLLING. 


379 


seven  to  twelve  feet  in  length.     The  excentric  a  is  generally  fast- 
ened upon  the  main  shaft,  or,  if  such  is  not  accessible,  upon  any 

Fig.  126. 


Portable  hand-shear. 

other  strong  and  well-supported  shaft.     The  foundation  must  be 
very  firm,  and  not  inferior  in  solidity  to  the  roller  trains.    The  steel 

Fig.  127. 


Shear  moved  by  an  excentric. 

blades  are  made  of  good  shear  or  cast  steel,  tightly  fitted  into  the 
cast  iron  lever  and  standard,  and  screwed  on  with  screw  bolts. 
For  the  cutting  of  heavy  bar  and  rough  bar,  the  standard  block  is 
generally  placed  very  low,  about  a  foot  above  ground ;  but  for  cut- 
ting common  bar  and  sheet  iron,  it  is  raised  from  two  feet  to  thirty 
inches  above  ground.  If  sheet  iron  is  principally  brought  to  the 
shears,  an  iron  frame  #,  5,  as  high  as  the  lower  cutter,  is  to  be  fast- 
ened to  the  standard.  Upon  this  frame,  the  sheet  is  moved.  In  work- 
ing sheet  iron,  shears  of  this  construction  are  attended  with  some 
disadvantage.  The  acute  angle  at  the  points,  and  the  obtuse  angle 
close  to  the  fulcrum  which  they  form,  in  addition  to  the  difficulty  of 
adjusting  them  accurately,  make  them  somewhat  objectionable. 


380  MANUFACTURE   OF   IRON. 

To  obviate  these  disadvantages,  various  plans  have  been  devised, 
of  which  the  following,  Fig.  128,  appears  to  be  the  most  prac- 

Fig.  128. 


Shear  moved  by  a  crank. 

ticable.  These  shears  are  generally  used  for  cutting  nail  plates, 
and  for  trimming  sheet  iron.  The  cutters  6,  b  are  shown  in  section, 
and  are  frequently  from  sixteen  to  twenty  inches  in  length,  so  as 
to  cut  over  the  entire  breadth  of  a  sheet ;  the  same  length  is  required 
where  sheet  iron  is  used  for  making  nails.  In  case  small  nail  plates 
are  used,  shorter  cutters  can  be  employed.  The  lower  or  fixed  cut- 
ter is  horizontal,  but  the  upper  is  screwed  to  the  cast  iron  lever  in 
such  a  manner  as  to  form  an  angle  with  the  lower  cutter  seldom 
greater  than  fifteen  degrees.  The  motion  of  the  lever  can  be  produced 
by  an  excentric,  as  in  Fig.  127,  or  by  a  crank,  as  in  the  present  case. 
It  frequently  happens  that  shears  are  wanted  where  we  cannot 
reach  directly  to  an  excentric  with  a  lever,  nor  in  a  short  way  with 
a  crank.  In  such  cases,  a  crank  motion  from  some  shaft  is  con- 
ducted below  ground  to  the  desired  point  by  means  of  an  iron  con- 
necting rod.  This  arrangement,  which  may  be  modified  accord- 
ing to  circumstances,  is  exhibited  by  Fig.  129.  The  tail  may  be 
turned  above  or  below  ground,  forward  or  back ;  but  care  should 
be  taken  that  the  connecting  rod  is  always  on  the  pull  side,  as 
shown  in  the  drawing,  for  a  long  connecting  rod  is  not  adapted  to 
push  the  lever.  This  arrangement — in  which  the  shears  are 
directly  connected  with  the  elementary  power — is  necessary  where 
heavy  bar  iron  and  boiler-plate  are  to  be  cut,  for  these  require  a 
strong  foundation.  Portable  shears,  with  their  own  independent 
flywheel,  propelled  by  means  of  a  belt  and  pulley,  are  preferable 
for  light  iron,  sheet  iron,  or  nail  plates.  Bar  iron  more  than  two 
inches  square  cannot  be  conveniently  cut  by  shears;  like  railroad 
iron,  this  is  to  be  trimmed  by  circular  saws. 


FORGING  AND  ROLLING. 

Fig.  129. 

^mfflllllllM 


381 


Shear  moved  by  a  crank. 

d.  The  method  of  fastening  the  steel  cutters  to  the  castings  by 
means  of  screw  bolts  passing  through  the  steel  blades,  is  exposed 
to  several  serious  objections.  In  this  way,  the  blades  are  weakened, 
and  screws  and  cutters  frequently  broken.  Strong  blades  would 
meet  the  emergency,  but  cannot  be  successfully  fastened  by  screw 
bolts.  If  designed  for  heavy  work,  the  cutter  should  be  very  strong, 
and  formed  of  a  solid  piece  of  steel,  from  an  inch  and  a  quarter  to 
an  inch  and  a  half  thick,  four  inches  wide,  and  eight  inches  long. 
By  fitting  such  a  piece  of  steel  carefully  into  the  cast  iron,  and  hold- 
Fig.  130. 


Screwing  in  the  cutters. 

ing  it  by  means  of  steel  screw  bolts,  as  represented  by  Fig.  130,  it 
may  be  conveniently  and  securely  fastened. 


3-82  MANUFACTURE    OF  IRON. 

X.  Tools. 

The  tools  required  in  a  rolling  mill  are  of  some  importance,  and 
absorb  considerable  means  in  their  outfit  and  repair.  The  principal 
tools  are  tongs,  which,  in  an  extensive  establishment,  are  very  nume- 
rous. A  set  of  tongs  belongs  to  each  re-heating  furnace,  compris- 
ing long  tongs  for  the  catching  of  small  billets,  and  tongs  for  heavy 
piles.  A  set  is  placed  before  and  behind  each  set  of  rollers,  which 
are  shorter  than  those  at  the  re-heating  furnace.  A  different 
kind  from  the  above,  from  three  to  four  feet  long,  belong  to  the 
heating  ovens,  and  short,  narrow  tongs  are  necessary  at  the  sheet 
rollers.  The  tongs  of  a  rolling  mill,  and  the  manner  in  which  they 
are  kept,  show  in  a  great  measure  the  character  of  the  establish- 
ment. Light,  well-made  tongs,  calculated  to  answer  their  different 
purposes  as  well  as  possible,  kept  in  good  repair,  and  in  sufficient 
number,  indicate  a  well-managed  mill.  Clumsy,  heavy  tongs 
roughly  made,  in  bad  repair  and  in  insufficient  number,  are  a  sure 
sign  that  something  is  wrong  in  the  management  of  the  mill; 
and,  by  close  investigation,  we  shall  find  similar  deficiencies  in  all 
the  other  departments  of  the  establishment.  To  make  good  and 
light  tongs,  sound  and  strong  iron  is  required.  Strong  shear  steel  is 
the  best  material  for  making  light  and  elegant  tools.  But  where 
the  steel  is  short,  it  is  advisable  to  pile  steel  and  good  charcoal 
iron  alternately.  The  resulting  metal,  drawn  into  bars,  will  make 
a  kind  of  Damascus  steel,  of  great  cohesiveness,  from  which  light 
tongs  of  the  most  elegant  form  may  be  wrought.  A  number  of 
hammers,  sledges,  and  wrenches  are  also  required.  At  each  re- 
heating furnace,  there  must  be  a  water  trough,  supplied  constantly 
by  a  current  of  cold  water,  for  the  purpose  of  cooling  the  tools. 
From  three  to  four  hooks,  five  or  six  feet  long,  and  lighter  than  those 
at  the  puddling  furnaces,  belong  to  a  re-heating  furnace;  also  a 
couple  of  pointed  bars  for  turning  the  piles.  Piles  composed  of 
bars  are  to  be  turned  as  soon  as  the  heat  of  the  furnace  is  suffi- 
ciently strong  to  make  them  adhere. 

Small  rod  iron,  hoops,  and  some  kind  of  wire,  are  put  up  in 
bundles  of  fifty  or  one  hundred  pounds'  weight  each,  on  a 
bench  constructed  for  the  purpose.  The  rods  of  small  iron  are 
first  weighed;  a  parcel  of  the  desired  weight  is  then  put  upon  the 
bench,  into  iron  standards,  and  there  tied  together  by  iron  hoops. 
The  bench  is  a  table  eighteen  or  twenty  feet  long,  two  or  three 
feet  wide,  and  made  of  plank  three  inches  thick.  Wrought  iron 


FORGING  AND  ROLLING.  383 

stands,  in  the  form  of  a  V,  are  fastened  at  such  distances  from  each 
other  as  to  suit  the  convenience  of  the  binders,  say  from  two  to 
four  feet.  To  one  leg  of  the  stand,  a  small  lever  about  a  foot  or  a 
foot  and  a  half  long  is  fastened;  it  is  pressed  upon  the  bundle  of 
iron,  forced  down,  and  locked.  A  binder  of  small  square  or  round 
iron  is  then  fastened  in  that  place.  These  binders  are  generally 
tied  when  heated ;  but,  in  many  establishments,  they  are  tied  cold 
around  the  bundle.  Generally  three  binders,  seldom  four,  are  fast- 
ened to  one  bundle.  Hoops,  and  small,  well-polished  rod  iron 
ought  to  be  handled  by  the  workman  in  gloves,  particularly  in 
summer;  for  clean  iron  has  a  fine  appearance. 

XI.   General  Remarks. 

a.  Where  the  country  is  settled  and  densely  populated,  there  is 
generally  a  large  demand  for  iron,  and  competition  and  large  estab- 
lishments have  so  reduced  its  price  that  a  profitable  employment 
of  Catalan  fires  cannot  be  expected.     But,  in  less  settled  coun- 
tries, where  wrought  iron  for  farming  purposes  is  in  demand,  and 
where  rich  ores  are  accessible,  the  Catalan  forge  is  profitable  from 
the  fact  that  but  a  small  capital  is  required  to  start  it.      The 
machinery  can  be  made  very  cheaply,  if  a  water  power  is  at  our 
disposal;  and  even  a  steam-engine  costs  but  little.     A  hammer 
150  or  200  pounds  in  weight  is  sufficient  to  do  a  great  deal  of  work, 
at  least  work  for  two  fires,  and  will  draw,  every  week,  from  five  to 
six  tons  of  iron,  if  the  rods  are  not  smaller  than  horse-shoe  bars 
or  wagon-tires.     From  good  ore,  the  iron  made  in  the  Catalan 
forge  is  preferable,  for  agricultural  purposes,  to  any  other  kind  of 
iron.     The  expenses  of  erecting  this  forge  cannot  be  stated  with 
precision ;  but  they  depend  on  locality,  industry,  and  the  kind  of 
iron  wanted.     A  Catalan  forge  may  be  put  in  operation  at*  an  ex- 
pense of  500  dollars ;  but  ten  times  that  amount  may  be  laid  out 
to  advantage.     As  the  main  body  of  materials  required  are  timber 
and  stones,  its  erection,  in  a  new  country,  where  timber  is  abun- 
dant, cannot  cost  a  great  deal.     Hardly  any  stock  of  coal  or  ore  is 
needed ;  and  the  ore  and  coal  worked  to-day  may  be  turned  into 
iron  and  cash  to-morrow. 

b.  Very  little  bar  iron  is  drawn  in  the  charcoal  forges,  and  that 
which  is  made  is  horse-shoe,  tire,  or  heavy  bar  and  pattern  iron. 
For  all  these  purposes,  cast  iron  hammers  and  anvils,  if  made 
of  good  cast  metal,  are  sufficiently  hard  and  smooth.     But  if  we 
want  to  draw  fine  iron  or  steel,  wrought  iron  hammers  and  anvils, 


384  MANUFACTURE   OF   IRON. 

furnished  with  well-hardened  and  polished  steel  faces,  are  neces- 
sary. It  is  difficult  to  weld  steel  to  a  large  piece  of  iron,  with- 
out spoiling  the  steel ;  it  is,  therefore,  more  profitable  to  insert  the 
steel,  in  a  separate  piece,  into  a  groove  made  in  the  hammer  face, 
and  in  the  anvil,  and  to  fasten  it  by  means  of  wedges.  Such  a  piece 
may  be  of  the  best  kind  of  cast  steel,  and  very  highly  polished, 
without  running  the  risk  of  breakage  or  loss  of  lustre.  The  more 
strokes  a  hammer  makes  in  a  minute,  and  the  lighter  the  hammer 
and  the  more  polished  the  faces,  the  greater  lustre  the  surface  of  the 
rod  will  show.  The  exclusion  of  oxygen  from  the  heating-oven, 
and  water  from  the  anvil,  will  impart  a  uniform  blue,  or  dark  violet 
color  to  the  iron.  If  we  want  a  fine, 'polished  surface,  and  a  good 
color,  the  iron  must  be  heated  in  an  oven,  upon  charcoal,  by  a 
low  heat,  with  the  utmost  exclusion  possible  of  atmospheric  air; 
the  coals,  burning  in  a  very  suffocated  fire,  will  form  only  carbonic 
oxide;  the  surface  of  the  iron  or  steel  will  thus  be  prevented  from 
oxidizing. 

c.  In  rolling-mills,  iron  is  rolled  and  drawn  to  one-fourth  of  an 
inch  in  diameter,  whether  round,  or  square.  Smaller  iron  is  drawn 
from  the  above  in  the  wire  mills,  by  passing  the  rods  through  holes 
made  in  steel  plates.  Hoop  iron  is  made  as  small  as  five-eighths 
of  an  inch  wide,  and  one  thirty-sixth  of  an  inch  thick.  In  former 
pages,  we  have  spoken  of  the  quality  of  iron  required  to  manufac- 
ture small  iron  to  advantage;  it  is  only  necessary  to  remark  here, 
that  the  rollers  and  re-heating  furnaces  are  to  work  in  such  perfect 
harmony,  that  the  least  loss  of  time  in  taking  out  the  iron  from  the 
furnace  must  be  obviated.  The  quantity  of  the  iron  not  only  suffers, 
but  its  quality  also,  if  it  is  too  long  exposed  to  the  influence  of 
the  flame  in  the  re-heating  furnace.  The  iron  loses,  with  its  car- 
bon, its  strength  and  lustre ;  it  looks  dull,  and  is  more  or  less  rotten, 
or  cold-short.  We  would  repeat  here  the  remark  formerly  made, 
that,  if  we  want  the  iron  to  have  finely  polished  surfaces,  we  must 
employ  hard  and  well-polished  rollers ;  for  the  lustre  of  the  manu- 
factured article  cannot  be  greater  than  the  polish  of  the  rollers  from 
which  it  receives  its  impression.  A  train  of  five-inch  rollers  ought 
to  make,  in  a  week,  from  twenty  to  twenty-five  tons  of  small  iron, 
with  a  loss  of  not  more  than  ten  per  cent,  of  iron  if  made  directly 
from  rough  billets,  and  of  not  more  than  seven  or  eight  per  cent, 
if  rolled  from  merchant  bars.  The  amount  of  coal  consumed,  whe- 
ther anthracite  or  bituminous,  does  not  exceed  half  a  ton  to  each 
ton  of  iron. 


FORGING  AND  ROLLING.  385 

d.  Iron  of  first  rate  quality  is  not  required  for  the  manufacture 
of  hoop  and  small  rod  iron;  any  cold-short  iron  will  answer.    For 
particular  purposes,  such  as  the  making  of  small  chain  rods,  a  fine- 
grained, yet  cold-short,  iron  is  preferable,  unless  we  design  the 
rods  to  be  fibrous.    Cold-short  iron  is  to  be  preferred  for  small  ar- 
ticles made  by  the  blacksmith,  on  account  of  its  welding  properties. 
We  do  not  mean  to  say  that  an  excess  of  silicon  or  phosphorus  is 
not  hurtful  to  small  iron ;  on  the  contrary,  we  wish  it  to  be  under- 
stood that  such  matter  is  very  injurious.     Iron  containing  a  small 
amount  of  silicon  or  phosphorus,  and  sufficient  carbon  to  make  it 
cold-short,  is  the  most  profitable  for  the  manufacture  of  small  iron, 
as  well  as  for  blacksmiths'  use.     The  kind  of  iron  needed,  in  this 
case,  may  be  considered  the  connecting  link  between  the  quality 
necessary  for  making  heavy  iron  and  that  for  making  wire. 

e.  Wire  iron  should  be  strong,  hard,  and  tough.     That  which  is 
fibrous,  but  not  strong,  is  of  no  use;  the  wire  made  from  it  will  be 
rotten,  and  without  lustre.     Where  fibrous  iron  is  employed  for  this 
purpose,  the  fibres  must  be  very  fine,  and  the  color  of  the  iron  white. 
If  the  iron  is  bright,  coarse  fibres  make  rough,  scaly  wire;  but  if  it 
is  fibrous,  and  of  a  dull  color,  the  wire  will  be  both  rough  and  rotten. 
Iron  rendered  cold-short  by  silex  or  phosphorus  is  not  adapted  for 
wire  manufacture;  but,  when  rendered  cold-short  by  carbon,  it  will 
form,  for  this  purpose,  the  most  advantageous  material  available. 
Iron  which  is  hot-short  on  account  of  sulphur  is  very  apt  to  break 
in  drawing.     That  which  is  hot-short  in  consequence  of  a  deficiency 
of  impurities  is  a  still  worse  article.    Very  pure  iron  is  so  weak  that 
wire  cannot  be  made  from  it.    The  strongest  kind  of  wire  is  made 
from  an  iron  which  contains  just  sufiicient  copper  to  make  it  de- 
cidedly hot-short.    Wire  iron  must  be  very  uniform  in  its  aggregate 
form;  that  is,  the  billets  from  which  wire  is  to  be  drawn  must  have 
a  uniform  texture  throughout.    It  must  not  be  a  conglomeration  of 
fibrous  iron,  cast  iron,  and  steel.     It  requires  dexterous  workmen 
to  make  a  good  article  even  from  excellent  metal.     The  Catalan 
forge  is  not  adapted  for  this  purpose,  even  though  the  iron  should 
be  the  product  of  the  best  of  all  materials;  it  does  not  work  with 
sufiicient  regularity.    White  coke  or  anthracite  metal  will  not  make 
wire  iron,  even  with  the  greatest  attention,  and  in  the  best  charcoal 
forge.     Very  nearly  the  same  may  be  said  of  hot  blast  and  white 
charcoal  metal  smelted  from  the  poorer  ores  of  the  coal  formation, 
and  bog  ores.     White  metal  from  the  rich  magnetic  ores  of  New 

25 


386  MANUFACTURE  OF  IRON. 

York,  New  Jersey,  and  Missouri,  answers  excellently,  if  carefully 
worked  in  a  charcoal  forge.  The  best  wire  iron  is  made,  in  the  pud- 
dling furnace,  from  cold-short  gray  charcoal  pig,  or  from  any  gray 
pig  iron,  whether  charcoal  or  anthracite,  provided  the  metal  is  of 
such  a  quality  that  no  difficulty  results  from  boiling  it.  Neither 
the  best  nor  the  inferior  qualities  of  white  metal  will  make  good 
wire  iron  in  the  puddling  furnace.  Iron  of  fine  grain,  or  fine  fibre, 
of  uniform  texture,  great  lustre,  and  of  a  somewhat  bluish  color, 
and  soft  as  well  as  very  tenacious,  is  that  upon  which  our  principal 
reliance  must  be  placed.  From  this,  it  is  evident  that  wire  iron  may 
be  most  profitably  made  in  puddling  works  where  boiling  is  well 
managed.  In  such  establishments,  the  finest  and  strongest  rough 
bars  may  be  reserved  for  wire  iron.  A  selection  may  be  more 
safely  made  from  billets  than  flat  bars ;  and  cold-short  is  to  be  pre- 
ferred to  fibrous  iron. 

/.  Iron  for  the  manufacture  of  railroad,  coarse  bar,  boiler-plate, 
and  common  sheet  iron,  is  to  be  of  a  different  texture  from  wire 
iron,  merchant  bar,  and  thin  sheet  iron.  That  which  is  designed  for 
these  purposes  is  exposed  to  the  heat  of  the  re-heating  furnace  in 
large  piles,  blooms,  or  slabs,  to  prevent  the  oxygen  of  the  flame  from 
abstracting  the  carbon  from  the  interior  of  the  pile  so  soon  as  would 
otherwise  be  the  case.  It  should  be  white  and  fibrous  in  the  rough 
bars ;  otherwise,  it  will  be  very  cold-short  by  the  time  it  is  trans- 
formed into  the  proper  shape.  Another  reason  why  such  iron  should 
be  fibrous  and  white  is  that  cold-short  iron,  re-heated  in  heavy 
piles,  is  liable  to  great  loss  in  the  furnace.  Before  the  interior  of 
the  pile  can  be  heated  to  a  welding  heat,  the  exterior  is  melted  and 
wasted.  The  iron  most  liable  to  loss  in  the  re-heating  furnace  is 
the  very  best  and  finest.  To  avoid  this  waste,  and,  at  the  same 
time,  to  secure  a  perfect  heat,  heavy  piles  are  composed  of  different 
qualities  of  iron.  The  top  and  bottom  bars  are  generally  refined 
mill  bars,  or  a  superior  quality  of  rough  bars.  Mill  bars  will  resist 
a  higher  and  a  more  prolonged  heat  than  rough  or  puddled  bars,  and 
are,  therefore,  commonly  employed.  A  pile  thus  formed — that  is, 
composed  inside  of  iron  which  can  be  welded  by  a  lower,  and 
outside  of  iron  which  requires  a  higher  heat — will  answer  best  with 
respect  to  quantity.  Of  quality  we  shall  speak  hereafter.  For 
heavy  work,  the  iron  must  resist  a  high  heat,  and  often  a  heat  of  long 
duration.  For  these  reasons,  we  require  white,  fibrous  iron.  Iron 
which,  in  consequence  of  the  absence  of  carbon  or  other  matter,  is 
not  cold-short,  is  advantageous.  Such  iron  requires,  and  will  bear, 


FORGING   AND  ROLLING.  387 

a  higher  heat  for  welding  than  that  which  is  less  white  and  less 
fibrous.  At  the  same  time,  it  will  yield  better,  and  not  waste 
away  so  fast.  Therefore,  in  selecting  qualities  of  rough  bars  for 
the  different  purposes  of  the  merchant  mill,  iron  of  fine  grain  or 
fine  fibre  must  be  chosen  for  the  lightest  kind  of  rod  iron,  such  as 
wire  and  small  rod ;  coarser,  though  not  fibrous,  iron,  for  hoops 
and  all  kinds  of  flat  iron ;  fibrous  iron  of  a  dark  color  for  square 
and  round  merchant  bar ;  and  white  fibrous  iron  for  heavy  bar, 
boiler-plate,  and  railroad  iron. 

g.  The  piling  of  iron  for  the  re-heating  furnace  is,  as  far  as 
quality  and  quantity  are  concerned,  an  object  of  the  utmost  im- 
portance, and  too  much  attention  cannot  be  paid  to  it.  In  a  well- 
managed  rolling  mill,  every  rough  bar  is  tested,  and  classified  ac- 
cording to  its  texture.  All  the  iron  may  be  equally  good,  the 
grained  equal  to  the  fibrous  ;  but  the  texture  of  the  rough  bars  has 
an  influence  upon  the  quality  and  quantity  of  the  article  made  from 
them.  These  bars  must  be  straight,  to  admit  of  close  packing, 
and  they  are  to  be  sound  and  smooth  on  all  sides,  to  offer  a  com- 
pact and  close  surface  to  the  influence  of  the  flame.  Cold-short  is 
more  easily  welded  than  fibrous  iron ;  and  dark  iron  will  adhere 
together  at  a  lower  temperature  than  white  iron.  This,  of  course, 
is  to  be  applied  to  iron  made  from  the  same  metal,  and  in  the  same 
forge.  Accordingly,  the  puddled  iron,  or  rough  bars,  are  to  be 
classified  into  grained  or  cold-short,  dull  or  dark  fibrous,  and  bright 
or  white  fibrous  iron.  The  second  is  the  worst  class ;  the  first  is 
designed  for  small,  and  the  latter  for  heavy  iron.  These  classes 
ought  to  be  kept  separate,  and  mixed  at  the  re-heating  furnace  ac- 
cording to  the  kind  of  pile  made,  or  the  commercial  iron  which  is 
to  be  manufactured  from  it. 

It  is  easily  understood  that,  on  the  piling  of  the  rough  bars,  suc- 
cess in  a  great  measure  depends.  If  it  should  happen  that  cold- 
short or  dark  iron  were  put  at  the  outside,  or  bottom,  or  top  of  a 
pile,  it  is  very  clear  that  the  outside  would  be  melted  and  wasted 
before  the  inside  could  be  welded.  The  same  happens  if,  acci- 
dentally, all  the  bad  iron  is  on  one  side  of  the  pile,  and  all  the  good 
on  the  other.  This  matter  ought  never  to  be  left  to  accident,  but 
it  should  be  regulated  with  reference  to  the  quality  of  the  iron. 
Heavy  piles  of  rough  bars  for  re-heating  are  to  be  composed,  in  the 
centre,  of  the  weakest  iron ;  at  the  bottom,  of  that  next  in  quality ; 
and  on  the  top,  of  the  best.  Or,  if  there  are  but  two  classes,  then 
the  weaker  at  the  bottom,  and  the  stronger  on  the  top.  Where  bar 


388  MANUFACTURE   OF  IRON. 

iron,  weighing  from  50  to  150  pounds,  is  to  be  made,  it  is  most 
advantageous  to  mix  the  metal  alternately,  that  is,  to  change  with 
each  single  bar,  so  that  not  more  than  one  bar  of  each  class  is 
joined  by  that  of  the  next  class.  A  uniform  mixture  will  thus  be 
made,  and  the  best  iron  produced  which  can  be  made  from  the 
quality  in  question.  If  we  reflect  upon  the  difference  which  exists 
in  iron  of  the  same  quality,  but  of  different  form  of  aggregation, 
with  respect  to  welding  at  a  high  or  a  low  heat ;  that  cold-short 
iron,  made  from  the  same  metal,  will  waste  away,  while  the  fibrous 
iron  is  not  yet  sufficiently  hot  for  welding;  if  we  further  reflect  upon 
the  accidental  running  together  of  one  or  the  other  class  of  iron,  in 
the  same  pile  or  the  same  heat,  irregularly,  which  cannot  be  avoided 
where  the  rough  bars  are  not  tested  and  classified,  we  must  not 
wonder  when  we  see  one  pile  yield  ninety-five  per  cent.,  while  the 
other  makes  but  eighty ;  or  when  we  see  the  splitting  of  blooms  or 
the  falling  off  of  pieces  in  the  roughing  rollers.  If  each  pile,  as 
we  have  stated,  is  thus  composed  of  a  systematical  range  and 
quality  of  rough  bars,  the  yield  is  uniform  in  the  single  piles,  and 
of  course  better  in  the  whole.  There  is  then  no  splitting  of  piles, 
or  waste  in  the  rollers.  This  is  always  true,  whether  the  manufac- 
tured iron  be  of  the  worst  or  the  best  kind,  the  weakest  or  the 
strongest.  All  iron,  if  uniform,  no  matter  what  its  quality  may  be, 
yields  better  and  works  better  than  it  would  under  other  circum- 
stances. A  pile  of  dull,  weak,  fibrous  iron  will  be  wasted  away  in 
a  temperature  scarcely  strong  enough  to  heat  a  good  charcoal  bloom 
sufficient  for  drawing,  much  less  for  welding.  How  imprudent  would 
it  be  to  put  such  different  kinds  of  iron  together  in  the  same  heat ! 
We  can  very  easily  conceive  the  result  of  an  attempt  to  weld  a  flat 
rough  bar  of  weak  puddled  iron  to  a  bloom  of  good  white  charcoal 
iron,  without  making  the  experiment.  The  weak  iron  will,  of 
course,  be  wasted  before  a  heat  sufficient  for  welding  is  raised.  It 
is  unprofitable  to  weld  weak  iron  to  strong  iron.  It  is  a  generally 
known  fact  that  we  can  unite  iron  of  the  same  texture,  whether  weak 
or  strong,  with  the  smallest  possible  loss.  These  remarks  we  deem 
sufficient  to  awaken  more  general  attention  to  the  classification  of 
rough  bars  than  is  paid  to  it  at  present.  Where  iron  is  puddled 
from  white  or  refined  plate  iron,  the  difference  is  not  so  striking  as 
in  establishments  where  gray  pig  is  boiled.  The  difference  is  most 
apparent  where  boiling  and  puddling  are  carried  on  in  the  same 
mill,  as  at  Pittsburgh,  and  at  almost  all  the  Western  puddling  es- 
tablishments. 


FORGING  AND  ROLLING.  389 

h.  An  object  of  considerable  importance  is  the  manufacture  of 
sheet  iron;  this,  as  well  as  bar  iron,  is  generally  made  in  the  same 
establishment.  So  long  as  charcoal  iron  is  used  in  the  manufacture 
of  sheet  iron,  which  is  commonly  the  case,  it  does  not  make  much 
difference  where  the  latter  is  made.  But,  if  it  is  to  be  manufac- 
tured from  puddled  iron,  it  is  of  some  consequence  to  use  iron  of  a 
particular  quality.  A  fine,  fibrous,  tenacious  iron,  of  a  bluish  color, 
though  not  too  white,  is  required.  Hot-short  iron  is,  of  all  kinds, 
the  very  worst,  because  it  splits,  and  gets  porous  and  scaly  in  the 
progress  of  the  manipulation.  Cold-short  is  not  good  for  heavy,  but 
answers  well  for  very  light  sheet  iron,  such  as  stove  pipe  ;  it  makes 
a  smooth  and  polished  surface.  Here,  as  well  as  in  the  manufac- 
ture of  bar  iron,  the  iron  is  to  be  classified  according  to  the  purposes 
for  which  it  is  designed.  Classification  is,  in  fact,  of  more  im- 
portance in  the  one  case  than  in  the  other.  The  price  of  sheet 
iron  justifies  the  application  of  better  pig  metal,  and  more  careful  and 
expensive  work  in  the  forge,  than  would  be  prudent  with  bar  iron. 
The  price  of  the  latter  is,  generally,  so  low,  that  a  scrupulous  ad- 
herence to  quality  is  scarcely  admissible.  Badly  worked  iron,  whe- 
ther from  the  charcoal  forge  or  the  puddling  furnace,  is  not  adapted 
for  the  manufacture  of  sheet  iron.  For  these,  and  many  other  rea- 
sons, sheet  and  bar  iron  ought  not  to  be  made  in  the  same  estab- 
lishment, and  from  the  same  kind  of  iron.  That  which  is  most 
profitable  for  bar  iron  will  make  neither  good  nor  cheap  sheet 
iron :  and  that  which  makes  the  best  and  cheapest  sheet  iron  is 
too  expensive  to  be  used  for  making  bar  iron.  Blooms  for  sheet 
iron  should  be  of  the  purest  and  best  kind  of  iron,  and  of  that  which 
is  most  free  from  sulphur,  silex,  and  phosphorus,  and  rendered  cold- 
short by  nothing  else  than  carbon.  For  light  sheet  iron,  cold-short 
iron  is  preferable,  because  it  works  easily,  and  takes  a  brilliant  and 
durable  polish.  It  does  not  oxidize  to  the  same  extent  as  a  more 
pure  and  fibrous  iron,  and  for  this  reason  takes  a  more  uniform 
color,  and  does  not  scale.  On  light  sheet  iron,  we  always  look  for 
a  rich,  bluish  color  and  high  polish.  Well-polished,  hard  rollers 
and  clean  iron  secure  any  degree  of  polish;  but,  to  succeed  well  in 
this  case,  a  particular  kind  of  iron  is  required,  which  separates  easily 
from  the  scales,  or  hammer-slag.  The  purest  iron  is  that  made 
cold-short  by  combination  with  a  little  carbon.  White,  fibrous  iron 
is  apt  to  form  thick  and  heavy  scales  of  hammer-slag,  which  ad- 
here strongly  to  the  iron,  and  are  deeply  impressed  in  its  surface. 
These  scales  are  removed  with  difficulty ;  acids  are  our  only  reli- 


390  MANUFACTURE   OF  IRON. 

ance,  because  many  small  particles  of  hammer-slag  are  so  deeply 
squeezed  into  the  iron,  that  nothing  short  of  solution  can  remove 
them.  After  their  removal,  such  sheet  iron  looks  rugged  and  un- 
even. Good  iron,  of  a  steel-like  grain,  if  properly  treated  in  the 
heating  oven,  does  not  form  these  thick  and  uneven  scales. 

To  make  heavy  sheet  from  cold-short  iron  is  an  unsafe  policy, 
for,  if  we  leave  the  quality  of  the  former  out  of  the  question,  its 
quantity  is  unfavorable.  Cold-short,  or  weak  iron,  if  rolled  from 
heavy  slabs  or  piles  into  boiler-plate,  is  very  apt  to  split  or  open  in 
the  centre;  this  is  a  great  loss,  for,  in  most  cases,  the  whole  sheet 
is  turned  into  scraps.  Besides  the  loss  caused  in  the  rollers,  we 
always  find  the  central  part  of  such  plates  very  weak,  scarcely 
better  than  cast  iron,  though  the  edges  may  be  good.  Heavy  sheet 
iron  and  boiler-plate  should  be  made  from  a  coarse,  fibrous,  white 
iron,  which  will  stand  a  high  heat  in  welding.  Boiled  iron,  and 
iron  from  hot  blast  worked  in  the  charcoal  forge,  are  unprofitable. 
Such  iron  will  either  spoil  the  sheet,  or  make  it  of  such  bad  quality 
that  it  would  be  dangerous  to  put  it  in  steam  boilers,  and  thus 
run  the  risk  of  destroying  human  life  and  property  by  explosion. 
Heavy  sheet  iron  should  be  made  from  blooms  which  are  manufac- 
tured, in  the  charcoal  forge  or  the  puddling  furnace,  from  white, 
and  the  very  best  kind  of  plate  iron  ;  or,  if  not  made  from  plate 
iron,  the  blooms  must  be  rolled  into  flat  bars,  piled,  re-heated,  and 
then  rolled  into  flat  mill  bars,  to  be  again  re-heated ;  this  is  repeated 
until  the  iron  assumes  a  strong,  fibrous  texture  and  a  bright  color. 
If  the  latter  cannot  be  produced,  it  is  necessary  to  reject  the  iron 
altogether,  at  least  for  the  manufacture  of  boiler-plate.  This  method 
of  refining  iron,  which  is  frequently  practiced  in  England,  is  too 
expensive  in  this  country;  and,  in  addition  to  being  expensive,  it 
is  ill  adapted  to  make  iron  of  proper  quality,  that  is,  strong  in 
every  direction.  It  will  be  strong  in  the  longitudinal  direction  of 
the  fibre  and  bars,  but  very  weak  in  the  transverse,  that  is,  across 
the  fibres.  Coarse,  weak,  fibrous  iron  is  to  be  considered  in  the 
same  light  with  respect  to  the  making  of  sheet  iron,  as  to  the  mak- 
ing of  wire.  The  sheet  from  such  material  will  be  porous,  scaly, 
and  weak,  and  will  not  answer  the  purposes  for  which  it  is  designed. 

In  the  erection  of  works  for  the  manufacture  of  sheet  iron,  too 
much  attention  cannot  be  paid  to  the  solidity  and  strength  of  the 
machinery,  and  to  a  surplus  of  power.  Success  depends  as  much 
on  an  unfailing  power  and  well-constructed  machinery  as  on  the 
well-trained  intellect  which  manages  the  daily  operations. 


FORGING  AND  ROLLING.  391 

«.  Nails  are  an  important  article  of  commerce,  and  an  item  in 
our  factories  which  must  be  regarded  with  due  attention.  For 
these,  good  iron  is  unnecessary ;  they  require  neither  strength  nor  the 
quality  of  welding,  which  are  two  requisites  of  iron  the  most  dif- 
ficult, at  least  the  most  expensive,  to  produce.  Nail  iron  must  be 
malleable,  that  is,  in  one  direction,  and  as  cheap  as  possible.  Sheet 
iron,  which  is  now  most  generally  employed  in  the  making  of  nail 
plates,  is  ill  adapted  to  make  a  cheap,  and,  at  the  same  time,  a 
good  nail.  So  long  as  good  charcoal  iron  is  used,  the  quality  of 
sheet  iron  is  secured:  but,  if  an  inferior  quality  of  charcoal  blooms* 
or  puddled  iron,  is  employed,  the  form  of  the  sheet  iron  does  not 
answer  so  well;  the  nails  will  be  cold-short,  though  made  from  an 
article  which,  for  the  manufacture  of  bar  iron,  would  be  highly 
useful.  In  New  England,  nail  plates  from  four  to  six  inches  wide, 
and  from  ten  to  thirty  feet  long,  are  made.  These  are  preferable 
to  sheet  iron;  that  is,  where  the  quality  of  iron  is  the  same,  a  far 
better  nail  can  be  made  from  these  plates  than  from  broad  plates  or 
sheet  iron.  As  previously  stated,  we  are  enabled  to  make  fibrous 
and  very  malleable  iron  from  almost  any  kind  of  pig  iron,  whatever 
its  quality  may  be,  provided  there  is  no  necessity  of  making  the  iron 
v,ery  cohesive,  or  of  giving  it  the  property  of  welding  in  the  black- 
smith's forge.  Such  iron  is  made  in  the  puddling  furnace  by 
a  very  low  heat,  and  it  must  be  re-heated  at  the  lowest  possible 
temperature;  otherwise,  it  will  lose  its  fibres  and  malleability, 
and  become  cold-short.  It  cannot  be  transformed  into  sheet  iron 
at  all ;  but  it  will  make  a  hoop  very  malleable  lengthwise,  though 
not  transversely  to  the  fibres.  It  cannot  resist  a  long-continued 
red  heat,  which  is  frequently  applied  at  the  nail  machine^,  with- 
out altering  its  fibrous  into  a  cold-short  texture.  Such  iron,  if 
well  worked,  is  generally  very  soft;  it  may  be  cut  when  cold, 
and  then  tempered  so  as  to  give  color  after  the  cutting  of  the 
nails.  This  is  a  proposition,  however,  not  based  upon  practice^ 
and  requires  confirmation.  Iron  of  this  kind  can  be  made  from 
pig  iron,  no  matter  how  bad  its  quality  may  be.  Puddling  does  not 
at  all  improve  its  purity;  it  only  alters  its  texture  from  a  granulated 
into  a  fibrous  aggregation.  Of  all  kinds  of  iron  it  is  the  cheap- 
est, for  it  is  worked  fast,  with  but  little  loss,  and  little  fuel ;  no  skill 
is  required  to  manufacture  it.  Industrious  work  and  the  lowest 
possible  heat  are  the  best  means  of  success  in  puddling.  Such  iron 
is  of  but  little  use  for  other  purposes,  but  we  verily  believe  it  will 
make  a  nail  far  superior  to  most  of  the  nails  at  present  in  market. 


392  MANUFACTURE   OF   IRON. 

To  make  nails  from  white,  coarse,  fibrous  iron,  however  strong  it  may 
be,  is  unprofitable,  for  the  nails  will  split,  and  cut  badly.  Such 
iron  is  of  too  good  a  quality,  and  is  better  adapted  for  making  coarse 
bar  or  heavy  sheet  iron.  Whatever  may  be  the  kind  of  iron  used 
for  making  nails,  it  is  always  better  to  draw  it  into  long  and  small 
nail  plates;  these  are  to  be  cut  into  strips  crosswise,  so  that  the 
nail  can  be  cut  parallel  with  the  length  of  the  plate  and  fibres.  The 
piles  for  making  nail  plates  are  to  be  put  together  with  due  regard 
to  the  production  of  the  most  perfect  fibres.  All  cross  piling  is  to  be 
avoided ;  and  if  cold-short  iron  is  to  be  worked  at  all,  it  must  be 
mixed  regularly  in  alternate  courses  with  fibrous  iron.  Such  piles 
may  be  very  heavy ;  the  greater  the  number  of  cuttings  of  rough 
bar,  the  better  will  be  the  result.  The  rolling  of  these  piles  is  to 
be  performed  in  such  a  manner  as  to  make  the  welding  joints 
parallel  with  the  surface  of  the  nail  plate.  In  the  re-heating  fur- 
nace, the  lowest  heat  commensurate  with  the  performance  of  the 
operations  is  the  most  profitable.  Any  heat  relatively  too  high 
will  transform  most  kinds  of  fibrous  iron,  particularly  this,  into 
cold-short  iron,  or  iron  of  a  crystaline  texture.  In  the  technical 
management  of  a  rolling  mill,  we  cannot  pay  too  much  attention 
to  the  classification  of  the  puddled  bars,  and  the  composition  of 
the  piles,  before  they  enter  the  re-heating  furnace. 


BLAST  MACHINES.  393 


CHAPTER  VI. 

BLAST  MACHINES. 

THE  principles  involved  in  the  construction  and  application  of 
blast  machines  are  based  rather  upon  the  chemical  effect  which 
a  strong  peculiar  draught  produces  in  burning  fuel,  than  on  any  me- 
chanical or  chemieo-physical  effect.  The  latter  effect  merely  in- 
creases the  consumption  of  fuel  in  a  given  space,  and  increases  the 
heat  in  that  space  to  a  limited  degree ;  but  the  former  causes  a  union 
of  the  oxygen  in  the  blast  with  the  fuel  or  carbon  in  a  manner  more 
or  less  favorable  to  the  reviving  of  iron  from  the  ore,  and  the  pro- 
tection of  the  iron  against  oxidation. 

The  means  to  effect  a  favorable  result  in  the  application  of  fuel 
for  the  purpose  of  augmenting  temperature,  as  in  puddling  and  re- 
heating furnaces,  and  heating  stoves,  are  various.  This  result  can 
be  accomplished  by  the  simple  application  of  chimneys,  or  of  blast, 
or  by  using  both  together.  Fuel  is  most  perfectly  used  where  it  is 
oxidized  in  the  highest  degree;  this  oxidation  takes  place  in  the 
re-heating  furnace,  where,  generally,  all  the  hydrogen  is  converted 
into  water,  and  all  the  carbon  into  carbonic  acid.  "We  cannot  say 
the  same  of  any  other  apparatus,  for  we  generally  find  a  mixture  of 
carbonic  oxide,  carbonic  acid,  and  free  oxygen,  which  is  an  evi- 
dence of  imperfect  combustion.  Increased  draught,  or  the  concen- 
tration of  more  heat  in  the  fire  chamber,  will  lessen  such  an  evil; 
but  there  is  frequently  a  deficiency  of  draught  in  cases  in  which 
heat  is  necessary,  as  in  that  of  the  puddling  furnace.  If,  in  such 
instances,  it  is  impossible  to  produce  sufficient  heat  by  the  draught 
of  the  chimney,  we  are  compelled  to  make  use  of  blast  machines. 
This  is  the  case  with  anthracite  coal  and  coke.  How  chimneys  act 
in  producing  draught,  and  what  are  the  rules  to  be  applied  in  con- 
structing them,  are  matters  which  require  scientific  demonstra- 
tion not  included  in  our  investigations.  We  have  described  the 
practical  workings  and  dimensions  of  apparatus,  which  may  be 
deemed  sufficient  for  all  practical  purposes.  An  explanation  as  to 


394  MANUFACTURE  OF   IRON. 

the  chemical  effect  of  blast  under  different  pressures,  we  shall  give 
at  the  close  of  the  chapter. 

There  are  many  forms  of  blast  machines;  but  in  our  own  country 
we  are  very  fortunately  reduced  to  the  most  simple  and  practical. 
We  shall  notice  some  blast  machines  in  operation  in  Europe,  which 
are  frequently  recommended  by  writers  on  metallurgy,  principally 
for  the  purpose  of  showing  their  imperfections.  The  most  simple 
blast  machine  is  the  smith's  bellows,  a  description  of  which  it  is 
unnecessary  to  give. 

I.  Wooden  Bellows  of  the  Common  Form. 
A  kind  of  blast  machine,  called  Widholm's  bellows,  is  very  ex- 
tensively used  in  Sweden,  Russia,  Germany,  and  France.  We  do 
not  know  that  any  are  employed  in  the  United  States.  As  it  works 
well,  as  the  expense  of  its  construction  is  small,  and  its  applica- 
tion to  the  Catalan  forge  very  simple,  we  shall  furnish  a  drawing 
and  description  of  it.  Fig.  131  shows  it  in  section;  a  is  the 

Fig.  131. 


Swedish  bellows. 

movable  part  or  piston ;  b  an  iron  rod  connected  with  a  crank  of  the 
waterwheel,  or  the  steam-engine ;  c,  c  are  the  valves,  and  d  the 
nozzle.  The  latter  is  fastened  to  the  permanent  top  /,  which  is 
again  fastened  to  some  wooden  framework.  The  whole  has  the  ap- 
pearance of  a  common  smith's  bellows,  with  the  only  difference 
that  it  is  made  entirely  of  wood.  From  ten  to  twelve  strokes  may 
be  made  in  a  minute,  and  two  bellows  are  required  for  one  fire. 
The  whole  is  from  six  to  seven  feet  long  and  thirty  inches  wide — 
the  piston  having  a  motion  of  twelve  inches.  This  kind  of  machine 
is  applied  to  no  other  apparatus  than  the  charcoal  forge,  and  we 
allude  to  it  merely  because  it  is  simple  and  cheap,  fulfilling  its 
purpose  excellently. 


BLAST  MACHINES. 


395 


II.    Wooden  Cylinder  Bellows. 

These  are  of  various  forms.  We  have  seen  square  cylinders  and 
round  ones  :  the  piston  playing  from  the  top,  or  from  below ;  or  the 
piston  working  in  both  directions.  There  are  vertical  and  horizon- 
tal cylinders,  and  machines  working  with  one,  two,  or  three  cylin- 
ders, with  a  dry  receiver,  water  receiver,  or  with  no  receiver. 

In  our  own  country,  we  are  almost  entirely  confined  to  one  prin- 
cipal form,  that  is,  the  machine  with  two  round  tubs  or  bellows — 
the  piston  working  from  below,  and  a  dry  receiver  placed  on  the 
top  of  the  tubs.  This  may  be  considered  the  best  form  of  the  wooden 
blast  machine,  if  but  a  single  stroke  is  desired.  Fig.  132  is  a  re- 
presentation of  a  blast  machine  of  this  kind;  a,  a  are  the  bellows; 

Fig.  132. 


Wooden  cylinder  bellows. 

b  the  receiver  from  which  the  sheet  iron  pipe  c  leads  the  blast  to 
the  furnace;  d,  d  are  the  pistons,  moved  alternately  by  the  beam 


396  MANUFACTURE   OF   IRON. 

/,  which  is  set  in  motion  by  the  crank  and  wheel  e.  The  wheel 
may  be  moved  either  by  a  waterwheel  or  a  steam-engine.  From 
eight  to  ten  strokes  is  generally  the  speed  required  to  supply  a 
charcoal  furnace.  The  tubs  or  cylinders,  as  well  as  the  receiver, 
are  generally  from  four  to  four  and  a  half  feet  wide,  and  four  feet 
high,  making  the  stroke  of  the  piston  three  feet.  To  the  piston  g, 
in  the  receiver,  an  iron  rod  is  fastened,  playing  in  a  stuffing-box 
at  the  bottom,  which  carries  a  box  h  filled  with  iron  or  stones,  to 
counterbalance  the  pressure  of  the  blast,  and  to  regulate  it  by  play- 
ing up  and  down  as  the  pressure  from  the  tubs  increases  or  di- 
minishes. The  valves  are  made  of  wood,  lined  with  leather.  The 
beam  is  generally  laid  below,  and  the  tubs  raised  a  few  feet  above, 
ground.  The  whole  machine  is  made  of  dry,  well-seasoned  wood 
— the  cylinders  glued :  that  is,  composed  of  small  segments  of  dry 
pine  or  ash,  an  inch  or  an  inch  and  a  half  thick  ;  the  woody  fibre 
thus  runs  around  the  cylinder,  i.  e.,  horizontally  instead  of  verti- 
cally. This  construction  of  the  tubs  secures  greater  permanency  to 
their  form.  Their  interior  is,  in  some  instances,  covered  with  a 
thin  coating  of  a  mixture  of  glue  and  plumbago,  which  gives  it 
the  appearance  of  iron,  diminishes  the  friction,  and  secures  a  closer 
fit  of  the  piston. 

This  kind  of  blast  machine  works  admirably,  if  properly  con- 
structed ;  it  is  very  durable.  In  every  respect,  this  apparatus  is 
preferable  to  the  wooden  bellows  of  the  common  form,  such  as  that 
represented  by  Fig.  131.  It  can  be  erected  at  an  expense  of  from 
$250  to  $350.  It  will  work  one  blast  furnace  for  charcoal,  or  from 
four  to  five  forge,  or  Catalan  fires.  A  steam-engine  or  waterwheel 
of  from  twelve  to  sixteen  horse  power  is  required  to  put  it  in 
operation,  and  furnish  the  necessary  blast  for  a  blast  furnace. 

a.  There  are  double  working  wooden  tubs  also  in  use,  but  not 
very  frequently.  These,  in  particular  cases,  may  be  of  advantage  ; 
in  cases,  for  instance,  where  room  or  expense  is  to  be  saved,  or 
where  wooden  are  very  shortly  to  be  replaced  by  iron  cylinders. 
The  wooden  tubs  are  but  a  temporary  arrangement,  to  gain  time 
and  means  after  the  works  are  just  started.  The  double  working 
tubs,  that  is,  those  which  make  blast  at  each  motion,  like  iron 
cylinders,  offer  no  real  advantages  over  the  single ;  in  fact,  in  ordi- 
nary cases,  the  tub  with  single  stroke  is  preferable  to  the  double 
tub.  Among  the  advantages  of  the  former,  is  the  facility  with 
which  we  can  attend  to  the  interior ;  in  case  damage  is  done  to  the 


BLAST   MACHINES.  397 

surface  of  the  tub,  it  can  be  instantly  mended.  This  is  notv  the 
case  with  double  stroke  cylinders ;  here  the  top  and  bottom  are 
closed,  and  the  interior  is  not  accessible  without  stopping  the  blast 
machine,  and  the  operations  which  depend  upon  it.  For  these 
reasons,  tubs  which  open  at  the  top  are  preferable  to  those  which 
open  from  below.  The  principal  objection  against  wooden  cylin- 
ders is  that  they  are  frequently  severely  rubbed  by  the  packing  of 
the  piston  ;  this  diminishes  the  pressure  of  the  blast  in  consequence 
of  the  leaking  between  the  piston  and  tub.  The  disadvantages 
resulting  from  single  stroke  tubs,  open  from  below,  are  more  than 
counterbalanced  by  the  greater  simplicity  of  the  piston  rod,  and  the 
facility  with  which  the  valves  can  be  adjusted.  A  stuffing-box  is 
required,  which,  if  the  tubs  are  to  be  opened  from  -above,  must  be 
made  of  iron.  The  expense  of  erecting  a  solid  and  strong  frame 
to  carry  the  crank  and  beam,  is  also  comparatively  great. 

b.  A  good  mechanic,  and  a  thinking  one,  is  required  to  construct 
a  wooden  blast  machine.  To  put  the  wood  well  together  is  not 
sufficient ;  it  is  necessary  to  select  it  with  due  relation  to  its  liability 
to  twist,  warp,  and  crack.  All  curly,  knotty  wood,  and  wood  from 
the  heart  of  the  tree,  must  be  rejected.  The  circumference  of  the 
tree,  or  both  seams  of  the  heart  plank  alone,  are  to  be  used  for  the 
tubs  and  receiver.  The  tops  as  well  as  the  tubs  are  generally  three 
inches  thick.  The  latter  are  glued  together  from  segments  one  foot 
or  more  in  length,  and  not  more  than  one  and  a  half  inch  thick,  as 
before  stated.  The  tops  and  pistons  are  composed  of  strips  of  plank 
not  more  than  three  or  four  inches  wide,  grooved  and  feathered, 
and  well  glued.  Ash  may  be  considered  the  best  wood  for  making 
the  tubs  ;  but  good  dry  pine  will  answer.  Other  kinds  of  wood, 
such  as  maple  and  walnut,  are  too  apt  to  warp,  and  therefore  ought 
not  to  be  used.  To  keep  the  interior  slippery  and  sound,  the  sur- 
face of  the  tub  is  frequently  brushed  over  with  plumbago,  or  soap- 
stone  powder,  or  with  a  mixture  of  both.  These  ingredients  are 
moistened  with  water,  to  which  a  little  glue  may  be  added.  Fat 
or  oil  is  an  improper  material  with  which  to  lubricate  the  surface  of 
a  wooden  tub,  for  both  are  very  soon  destroyed;  the  destruction  of 
the  piston  and  the  wood  of  the  cylinder  then  follows,  to  the  injury 
of  the  machine,  and  the  loss  of  blast. 

Square  tubs,  and  horizontal  tubs  of  double  stroke,  have  been 
tried ;  but,  it  appears,  with  no  good  advantage,  for  nobody  now 
thinks  of  such  forms.  It  is  unnecessary  to  speak  of  these  machines 


398 


MANUFACTURE   OF   IRON. 


in  this  place,  as  they  belong  to  antiquity,  and  are,  at  the  present 
time,  of  no  practical  importance. 

III.  Iron  Cylinder  Blast  Machines . 

a.  There  are  various  forms  of  these  machines.  The  smallest, 
but  not  the  most  simple,  apparatus,  is  a  double  stroke  cylinder — that 
is,  composed  of  two  beams  and  two  cylinders — which  is  frequently 
met  with  at  the  Western  establishments.  In  rolling  mills,  it  is  used 
to  blow  the  finery ;  we  find  it  also  at  blast  furnaces.  Fig.  133 

Fig.  133. 


Iron  cylinder  bellows. 

exhibits  it  so  plainly,  that  a  particular  description  of  it  is  unne- 
cessary. This  machine  makes  an  excellent  blast.  Its  cost  is  the 
main  objection  to  its  use ;  this  objection  is  valid,  as  far  as  the  first 
outlay  is  concerned;  but  its  expensiveness  is  counterbalanced  by  the 
excellent  manner  in  which  it  works.  It  does  not  make  quite  a  regu- 
lar blast,  if  worked  without  a  receiver  ;  but  even  in  this  case,  it  may 
be  made  to  work  better  frhan  others  differently  constructed.  In  this 
machine,  the  cylinders,  pistons,  pipes,  valves,  wheels,  and  cranks  are 
all  of  iron,  except  the  beams  and  pitmans,  which  are  of  wood;  but 


BLAST  MACHINES.  399 

the  latter  would  be  better  if  made  also  of  iron.  This  machine  is 
constructed  on  an  excellent  principle,  and  is  superior  to  the  hori- 
zontal cylinder,  very  much  used  in  the  Eastern  States.  This  is 
finding  its  way  to  the  Western  States,  which  does  not  augur  well 
for  the  speedy  and  successful  application  of  stone  coal  in  the  blast 
furnace  of  that  section  of  our  country. 

b.  The  desire  of  constructing  a  cheap  apparatus  has  led  to  the 
making  of  an  iron  cylinder  blast  machine  with  a  horizontal  instead  of 
a  vertical  motion  of  the  piston,  as  shown  in  Fig.  134.  There  is  no 
doubt  that  such  a  machine  is  far  cheaper  than  one  of  vertical  stroke; 
but,  when  we  consider  the  difficulty  of  keeping  the  packing  tight, 
and  the  loss  of  blast  which  thence  ensues,  and  the  frequent  disturb- 
ances which  originate  from  very  hard  rubbing  of  the  piston  on  one 
part  of  the  cylinder  alone,  it  may  be  doubted  whether  it  should  be 
considered  a  useful  apparatus;  in  fact,  experience  rather  bears 
against  than  confirms  its  utility.  Fig.  134  exhibits  such  a  cylinder. 

Fig.  134. 


Horizontal  cylinder  blast  machine. 

The  piston  rod  runs  through  both  heads,  to  carry  the  weight  of  the 
piston,  and  prevent  its  rubbing  with  all  its  strength  on  the  lower 
part  of  the  cylinder.  The  valves  are  generally  made  of  sheet  iron 
lined  with  leather.  Machines  of  this  construction  have  their  ad- 
vantages, besides  the  great  simplicity  in  their  entire  arrangement 
which  they  afford.  There  is  no  difficulty  in  procuring  a  solid 
foundation  for  the  whole.  The  weight  of  the  piston,  piston  rod, 
and  pitman,  which  is  objectionable  in  vertical  machines  propelled 
by  a  waterwheel,  particularly  in  those  where  but  one  cylinder  is  em- 
ployed, is,  in  this  case,  almost  balanced.  The  crank  and  a  small 
portion  of  the  pitman  form  the  only  weight  which  is  not  equipoised. 
The  application  of  the  valves  is  very  simple,  and  very  correct. 
They  must  be  suspended  vertically  in  a  good  blast  machine. 


400  MANUFACTURE  OF  IRON. 

The  foregoing  are  the  two  leading  arrangements  involved  in  the 
construction  of  blast  machines;  both  have  their  advantages  and 
disadvantages.  Where  the  propelling  power  is  a  waterwheel,  and 
where  it  is  contemplated  to  use  but  one  or  two  cylinders,  the  hori- 
zontal cylinder  may  be  considered  to  present  many  advantages;  for, 
in  such  cases,  it  is  always  more  or  less  troublesome  to  balance  the 
weight  of  the  piston,  rod,  &c.  If  the  motive  power  is  steam,  the 
vertical  position  of  the  cylinder  is  decidedly  preferable ;  for,  in  this 
case,  the  weight  of  the  piston  and  its  accompaniments  can  be 
balanced  by  the  weight  of  the  steam  piston  and  its  associated  parts. 
A  machine  consisting  of  one  blast  cylinder  and  a  receiver  may  here 
be  considered  the  most  simple  and  advantageous.  Where  a  water- 
wheel  is  the  propeller,  it  is  less  advantageous  to  employ  a  single 
cylinder,  for,  as  the  stroke  is  made  by  a  crank,  a  great  irregularity 
in  the  blast  ensues,  and  a  comparatively  large  receiver  is  there- 
fore required  to  regulate  the  inequalities  of  the  pressure.  This  is 
one  of  those  instances  in  which  a  crank  works  to  the  disadvantage 
of  the  power  applied,  which  is  seldom  the  case.  For  these  reasons, 
various  forms  of  blast  machines,  propelled  by  waterwheels,  have 
been  tried.  In  this  country,  however,  only  those  with  two  cylinders 
and  double  stroke  are  used.  This  makes  a  useful,  but  not  an  ex- 
cellent blast,  even  though  the  cranks  work  at  right  angles  to  each 
other.  A  receiver  is  almost  indispensable,  in  this  case,  to  equalize 
the  blast,  and  to  make  the  best  possible  use  of  the  water  power. 
Blast  machines  with  three  cylinders  and  double  stroke  have  been 
applied;  and  this  arrangement  may  be  considered  the  most  advan- 
tageous where  water  is  the  moving  power.  Such  a  machine  pro- 
duces a  very  steady  blast,  without  a  receiver,  and  gives  the  best 
effect  of  the  waterwheel. 

c.  There  is  no  reason  whatever  for  employing  water  power  in  the 
propelling  of  blast  machines  at  blast  furnaces.  There  is  abund- 
ance of  waste  heat  for  the  generation  of  steam.  The  expense  of 
erecting  a  steam-engine  will  be  found  less,  in  most  cases,  than  that 
incurred  in  the  erection  of  a  waterwheel.  For  these  reasons,  we 
shall  not  dwell  any  longer  upon  the  application  of  water  power 
to  blast  machines,  and  shall  confine  our  subsequent  remarks  to 
those  propelled  by  steam  alone. 

IV.  General  Remarks  on  Cylinder  Blast  Machines. 
There  is  no  doubt  that  the  application  of  one  cylinder  to  a  blast 
machine  is  accompanied  with  great  advantages.    Such  an  arrange- 


BLAST   MACHINES.  401 

ment  is  in  conformity  with  sound  principles  of  mechanics,  because, 
by  this  means,  the  least  friction  commensurate  with  the  same  effect 
is  produced.  Weight  and  surface,  the  two  most  important  causes 
of  friction,  are  very  greatly  reduced.  If  the  blast  cylinder  is  on 
one  end  of  a  balance  beam,  and  the  steam  cylinder  on  the  other, 
the  regularity  of  the  blast  is  much  greater.  But  this  is  no  reason 
why  a  balance  beam  should  be  applied :  because  any  inequality  in 
the  pressure  of  the  blast  can  be  regulated  by  applying  a  large  re- 
ceiver. If,  therefore,  it  is  found  advantageous  to  abandon  the 
balance  beam,  and  still  to  retain  the  vertical  position  of  the  cylin- 
ders, the  unbalanced  weight  of  the  pistons  and  piston  rods  is  no 
obstacle.  A  piston  rod,  to  connect  blast  and  steam  cylinders,  has 
been  applied  where  horizontal  cylinders  have  been  used — in  cases, 
however,  in  which  the  blunder  of  making  the  piston  rod  too  short 
was  committed.  The  hot  part  of  the  piston  rod,  playing  in  the 
steam  cylinder,  is  thus  cooled  when  in  the  blast  cylinder,  and  the 
adherent  oil  dried  when  playing  there.  By  this  means,  the  hemp 
of  the  stuffing  box  of  the  former  is  very  soon  worn  out.  Besides 
this  disadvantage,  the  close  proximity  of  the  steam  apparatus  and  the 
blast  cylinder  is  very  injurious  to  the  operations  in  the  blast  fur- 
nace. It  is  impossible  to  keep  the  steam  out  of  the  blast  cylinder, 
if  the  latter  is  too  close  to  the  steam  cylinder  or  the  steam  boilers, 
or  even  if  it  is  in  a  very  warm  place.  We  know  that  moisture  in- 
troduced into  the  hearth  of  a  blast  furnace  is  very  injurious. 

a.  The  size  of  a  blast  cylinder  depends  partly  on  the  amount  of 
air  needed,  and  the  number  of  strokes  made,  and  partly  upon  the 
purposes  for  which  it  is  designed.     A  charcoal  forge  requires  from 
400  to  500   cubic  feet  per  minute ;  a  finery  from  800  to  1000 ;  a 
charcoal  furnace  from  1000  to  2000 ;  and  an  anthracite  or  coke 
furnace  from  3000  to  5000.     The  number  of  strokes  that  can  be 
made  by  a  machine  depends  chiefly  on  the  length  of  the  stroke  and 
the  construction  of  the  valves.     In  cylinders  of  four  feet  diameter, 
the  piston  can  move  with  the  speed  of  three  feet ;  in  smaller  cylin- 
ders with  greater,  and  in  larger  ones  with  less   speed.     If  the 
motion  is  regulated  by  a  flywheel  and  crank,  more  speed  can  be 
given  than  where  a  flywheel  is  not  employed. 

b.  The  size,  form,  and  weight  of  the  valves  have  a  highly  im- 
portant influence  upon  the  speed  of  the  piston,  loss  of  power,  and 
quality  of  blast.     The  smaller  the  valves  are  made,  the  greater  is 
the  increase  in  the  velocity  of  the  air  which  is  to  pass  through  them. 

26 


402  MANUFACTURE    OF   IRON. 

Friction  of  the  air  and  valves,  besides  a  direct  loss  of  pressure  and 
air  in  proportion  to  the  pressure  in  the  valve,  is  thus  occasioned. 
One-twelfth  of  the  surface  of  the  piston  is  sufficient  for  the  passage 
of  the  blast ;  but  no  disadvantage  results  if  the  valves  are  larger. 
The  form  of  the  latter  has  an  influence  upon  the  effect  of  the  ma- 
chine. Trap  valves  are  the  most  practicable.  Semicircular  valves, 
with  the  hinges  in  the  diameter,  deserve  to  be  more  extensively  em- 
ployed than  they  are  at  the  present  time.  The  semicircle  has  less 
outline  in  proportion  to  the  same  surface  than  the  square  or  paral- 
lelogram, the  usual  form  of  valves,  and  for  this  reason  diminishes 
the  friction  of  the  air.  Quadrilateral  valves  are  seldom  used.  In 
general,  the  oblong  shape  is  preferred,  in  which  case,  the  hinges 
are  put  to  one  of  the  longest  sides.  It  is  obvious,  from  reasons 
which  will  be  subsequently  given,  that  the  longer  the  valve,  the  more 
perfect  will  be  its  form.  The  weight  of  the  valve  is  an  important 
object,  for,  if  neglected,  it  may  seriously  injure  the  effect  of  a  blast 
machine.  It  is  easily  understood  that  this  weight  may  be  so  in- 
creased, that  the  effect  of  a  blast  apparatus  amounts  scarcely  to 
anything.  The  weight  of  the  valve  causes  an  expansion  of  the  air 
in  suction ;  consequently,  the  pressure  on  the  suction  side  of  the 
piston  in  proportion  to  this  weight  will  be  less  than  that  of  the  atmo- 
sphere. A  loss  of  power  and  blast  on  the  compressing  side  of  the 
piston,  proportional  to  the  weight  of  the  valve,  is  also  occasioned. 
The  air  which  remains  in  the  dead  space  of  the  cylinder  is  of  greater 
pressure  than  that  in  the  blast  pipes  or  receiver,  in  the  ratio  of  the 
weight  of  the  valve.  To  diminish  the  influence  of  this  weight,  the 
valves  are  generally  placed  in  a  vertical  position,  and  are  made  en- 
tirely of  a  light  material,  such  as  wood  and  leather  ;  they  are  also 
made  as  oblong  as  circumstances  will  admit.  In  this  respect,  the 
horizontal  blast  cylinder  possesses  great  advantages.  The  location 
of  the  valves  is  best  secured  by  vertical  heads  ;  and  if  the  friction, 
or  rather  the  weight,  of  the  piston  and  piston  rod  could  be  balanced, 
the  horizontal  cylinder  would  be  the  best  form  of  the  blast  machine. 
Their  position  and  weight,  also,  have  considerable  influence  upon  the 
effect  of  a  blast  machine  ;  but  of  still  more  consequence  is  the  dead 
space  left  at  the  heads  of  a  cylinder.  Dead  space  is  that  which  is 
not  filled  by  the  piston  head,  in  its  alternate  motions,  and  from  which 
the  air  that  is  compressed  is  not  forced  by  the  piston.  In  the  best 
blast  machines,  the  loss  which  this  occasions  amounts  to  at  least 
ten  per  cent.,  and  in  some  cylinders  is  as  great  as  twenty-five  per 
cent.  The  loss  in  power  and  blast  increases  with  the  size  of  the 


BLAST   MACHINES.  403 

dead  space.     In  this  respect,  the  horizontal  has  the  advantage  over 
the  vertical  cylinder. 

<?.  There  are  advantages  connected  with  the  vertical  which  can- 
not be  reached  by  the  horizontal  cylinder,  namely,  a  closer  fit  of 
the  piston  head  to  the  cylinder,  and  less  friction,  as  well  as  smaller 
loss  by  leakage.  But  as  there  are  serious  objections  to  it,  on  ac- 
count of  dead  space,  and  of  the  position  of  the  valves,  we  shall  pro- 
pose an  improvement  to  the  vertical  cylinder  which  may  render  it 
more  acceptable.  In  a  vertical  cylinder,  we  cannot  well  place  the 
valves  at  the  top  and  bottom,  because  of  their  horizontal  position; 
horizontal  valves  are  thus  rendered  necessary.  In  small  cylinders 
the  valves  are  frequently  horizontal ;  but  large  valves  will  not  work 
well,  if  thus  laid.  To  secure  a  vertical  position  for  the  valves,  in  a 
vertical  cylinder,  we  are  compelled  to  add  valve  boxes  to  the  heads 
of  the  cylinder.  Such  boxes,  of  course,  obstruct  the  passage  of  the 
blast,  and  occasion  dead  space — disadvantages,  if  possible,  to  be 
avoided.  These  may  be  obviated  by  the  following  arrangement : 
If  the  stroke  of  the  piston  is  six  feet,  and  the  thickness  of  the  piston 
head  four  inches,  a  cylinder  six  feet  six  inches  long  is  required,  to 
secure  one  inch  space  at  each  end.  If  we  make  the  cylinder  seven 
feet  and  a  half  long,  instead  of  six  and  a  half,  a  dead  space  of 
fourteen  inches,  or  seven  inches  at  each  end,  would  be  left.  Around 
this  space,  and  in  the  metal  of  the  cylinder,  a  series  of  valves  may 
be  placed.  In  this  way,  the  number  of  valves  may  be  multiplied 
to  any  extent  we  choose.  The  blast  pipe  is  formed  by  screwing 
sheet  iron  or  boiler-plate  to  the  flanches  of  the  cylinders,  and  by 
covering  as  many  outlet  valves  as  we  choose  to  put  in.  The  dead 
space  caused  by  the  excessive  length  of  the  cylinder  is  occupied 
by  an  increased  thickness  of  the  piston  head ;  this  thickness  can  be 
produced  by  a  filling  of  light  pine  wood,  or  any  other  light  material. 
The  heads  of  such  a  cylinder  will  then  be  quite  smooth.  In  the 
following  illustration,  Fig.  135,  the  arrangement  is  so  clearly  exhi- 
bited that  no  further  explanation  is  required. 

d.  The  piston,  in  wooden  cylinders,  is  generally  packed  with 
leather,  or  hemp,  or  by  a  mixture  of  both;  also,  by  filling  leather 
hose  with  horse  hair  or  wool,  and  by  fastening  this  around  the  piston 
head  into  a  groove,  which  is  turned  in  the  circumference  of  it. 
Packing  in  iron  cylinders  is  performed  like  packing  in  steam  cylin- 
ders. A  steel  or  wrought  iron  hoop,  a  quarter  of  an  inch  thick,  is 
laid  around  the  piston  head,  and  the  space  between  the  hoop  and 
the  head  is  stuffed  with  hemp  or  woolen  material.  In  machines  with 


404  MANUFACTURE   OF  IRON. 

vertical  cylinders,  we  often  see  the  piston  rod  playing  from  above ; 
but  we  quite  as  frequently  see  an  arrangement  by  which  the  .piston 


Fig.  135. 


Blast  cylinder,  piston,  and  valves. 

is  made  to  move  from  below.     As  far  as  the  effect  of  the  machine  is 
concerned,  this  is  merely  a  consideration  of  expediency  and  economy. 

V.    Various  Forms  of  Blast  Machines. 

In  no  branch  of  human  industry  have  more  ingenuity  and  talent 
been  displayed  than  in  the  construction  of  blast  machines.  Still, 
the  greater  part  of  such  inventions  were  made  with  a  limited 
knowledge  of  their  purposes.  Hence,  an  imperfection  in  most  of  the 
plans,  though  apparently  well  conceived,  has  been  the  consequence. 
The  leading  principles  in  this  invention  were  generally  reduced  to 
the  mechanical  effect  of  the  aparatus,  that  is,  to  obtaining  the 
greatest  effect  from  a  given  power,  or  producing  the  greatest  amount 
of  blast  by  the  smallest  means.  Of  the  numberless  variety  of  blast 
machines  thus  invented,  there  is  but  one  which  deserves  our  atten- 
tion, in  addition  to  the  cylinder  machines  already  described.  This 
is  the  Cagniardelle,  or  screw  blast  machine.  Other  machines,  how- 
ever extensively  they  may  be  employed,  are,  for  our  purpose, 
scarcely  worth  notice:  they  may  serve  in  other  metallurgical  ope- 
rations, but  are  not  available  in  iron  manufactories.  Among  these, 
are  the  Trompe,  the  Rosary  or  Chain-trompe,  the  Water-column 
machines,  the  Gasometer  bellows,  and  Barrel  machines.  These 


BLAST  MACHINES.  405 

are  the  most  common  of  the  fancy  class.  As  there  may  be  many 
readers  "who  wish  to  know  more  than  the  names  of  these  machines, 
we  shall,  as  far  as  it  is  in  our  power,  give  a  description  of  them. 
We  have  gone  to  no  expense  for  engravings,  because  we  do  not 
think  the  whole  of  these  machines  worth  an  engraving. 

a.  The  trompe,  as  well  as  the  rest  of  this  class,  is  driven  by 
water;  in  fact,  the  water  forms  the  piston,  which  compresses  the 
air.     The  machine  consists  principally  of  two  vertical  pipes,  the 
length  of  which  is  equal  to  the  height  of  fall  or  head  water.    These 
pipes  are  slightly  tapered,  somewhat  wider  at  the  top  than  at  the 
bottom.    At  the  top  of  the  pipe  is  the  entrance  of  the  water ;  it  falls 
through  a  short  conical  pipe,  which  is  somewhat  narrower  than  the 
interior  of  the  main  pipe.    In  the  main  pipe,  behind  this  short  pipe 
or  nozzle,  are  holes  through  which  the  air  is  drawn,  which,  after 
mingling  with  the  water,  is  carried  with  the  latter  into  a  receiver; 
from  this  receiver,  the  water  flows  off,  and  the  air  is  collected  and  con- 
ducted in  another  pipe  to  the  furnace.    This  machine  is  based  upon 
the  same  principle  as  that  by  which  the  draught  in  the  chimney  of 
a  locomotive  is  produced.    If  we  turn  a  locomotive  chimney  upside 
down,  and  turn  water  in  at  its  top,  we  shall  have  a  trompe,  provided 
several  air  holes  are  made  in  the  chimney  around  the  nozzle,  and 
the  lower  part  of  it  is  set  into  a  receiver  which  will  retain  the  air, 
and  permit  the  water  to  flow  off. 

b.  The  rosary,  or  chain-trompe,  is  an  improvement  upon  the 
former.    There  is  but  one  vertical  pipe,  which  is  cylindrical,  as  wide 
at  the  base  as  at  the  top.     In  this  pipe  moves  an  endless  chain, 
over  two  pulleys,  one  at  the  top  and  the  other  at  the  bottom.    To 
this  chain,  at  certain  distances,  pistons  of  wood  or  leather  are  fast- 
ened, which  move  with  it.    If  the  head  water  is  led  into  the  pipe, 
where  are  always  several  pistons,  it  will  move  the  chains  and  pis- 
tons; and  the  pressure  of  the  blast  will  be  proportional  to  the  dis- 
tance between  the  pistons  and  the  fall  of  the  water.     The  air  is 
collected  into  a  receiver  in  the  same  manner  as  in  the  former  case. 

Water-column  machines,  of  the  most  curious  forms,  and  of  a  very 
complicated  nature,  have  been  invented.  A  great  deal  of  ingenuity 
has  been  wasted  upon  a  subject  which  will  never  reward  the  in- 
ventor. 

c.  Gasometer  bellows  are  constructed  like  a  common  gasometer; 
the  receiver  is  moved  up  and  down  by  the  engine,  and  by  that 
motion  blast  is  generated.     A  barrel-machine  is  a  cylinder  made 
of  wood,  resting  horizontally  in  its  longitudinal  axis.    Inside  of  the 


406  MANUFACTURE   OF  IRON. 

cylinder  is  a  partition  board  fastened  to  the  periphery  on  one  side, 
and  parallel  with  the  axis.  This  partition  divides  the  interior  into 
two  equal  parts.  The  barrel  is  half  filled  with  water,  into  which 
the  partition  board  partly  reaches.  In  the  heads  of  the  barrel  are 
the  valves  for  suction  and  compression.  If  this  barrel  is  moved  half 
way  around  its  axis,  the  air  in  the  space  between  the  surface  of  the 
water  and  the  partition  to  which  the  latter  is  moving,  will  be  com- 
pressed, and  form  blast.  Of  all  these  machines,  not  one  deserves 
attention,  because  in  all  of  them  the  air  which  forms  the  blast  is 
continually  in  contact  with  water  more  or  less  agitated,  which  of 
course  it  moistens  to  excess.  This  is  a  sufficient  reason  for  reject- 
ing them. 

d.  The  following  apparatus  suffers  under  the  same  disadvan- 
tages as  those  just  described,  namely,  that  its  blast  is  moistened, 
on  account  of  the  water  it  contains.  But  its  advantages  over  any 
other  machine  are  so  preponderating,  that  a  skillful  and  cultivated 
mind  may  be  advantageously  employed  in  perfecting  it.  For 

Fig.  136. 


Screw  blast  machine. 


this  purpose,  nothing  else  is  needed  than  to  replace  the  water 
by  some  liquid  which  is  not  injurious  to  furnace  operations. 
The  screw  blast  machine,  or  Cagniardelle,  is  represented  by  Fig. 
136.  A  is  a  copper  or  sheet  iron  hollow  cylinder,  resting  on  the 
two  necks  of  its  hollow  axis.  This  cylinder,  which  may  be  from 


BLAST   MACHINES.  407 

two  to  ten  feet  in  diameter,  is  furnished  inside  with  divisions, 
made  by  a  sheet  iron  spiral  or  screw,  which  is  fastened  to  and 
rotates  with  the  cylinder,  and  is  air-tight.  It  is  secured  to  the 
cylinder  and  the  axis.  The  head  b  is  straight ;  but  one  quarter  of 
it  is  open,  which  corresponds  with  the  interior.  The  head  c  is  a  kind 
of  conical  dome,  which  is  open  all  around  the  axis;  d  is  a  cast  iron 
pipe,  which  conducts  the  blast  from  the  interior  of  the  screw  to  the 
furnace,  and  the  end  of  it  within  the  cylinder  is  covered  with  a  kind 
of  cap,  to  prevent  the  falling  in  of  drops  of  water.  The  whole  ma- 
chine is  immersed  in  an  iron  trough,  filled  with  water  to  the  highest 
part  of  the  axis.  If  the  cylinder  a  is  turned  round  its  axis,  the 
opening  in  the  head  b  will  be  alternately  under  and  above  water ; 
the  first  cell,  which  is  formed  by  the  screw,  will  be  filled  with  water 
if  the  opening  is  immersed,  and  with  air  if  the  opening  is  above 
water.  The  air  and  water  in  the  interior  will  move  towards  the 
lowest  point  of  the  cylinder ;  the  latter  is  discharged  through  the 
opening  c,  and  the  first  through  the  blast  pipe  d.  The  pressure  of 
the  blast  corresponds  to  the  difference  between  the  water  levels  e  and 
ft  and  depends  upon  the  length  and  degree  of  inclination  of  the 
cylinder.  The  only  disadvantages  of  this  machine  are,  as  remarked 
above,  the  contact  between  the  air  and  water,  which  is  very  objec- 
tionable. Still,  as  we  have  stated  before,  its  advantages  are  numerous. 
All  is  very  simple ;  a  perfect  machine  with  rotary  motion;  no  valves, 
or  packing  of  piston ;  no  loss  of  air ;  very  little  friction ;  no  dead 
space;  it  gives  a  continual  stream  of  blast  of  uniform  pressure;  it 
gives  a  better  effect  than  any  other  blast  machine,  and,  finally,  the 
power  of  the  engine  is  applied  to  it  to  the  best  advantage. 

VI.  Fan  Blast  Machines. 

These  machines  are  very  common  in  the  anthracite  region  of 
Pennsylvania :  they  are  used  at  steam  boilers,  and  puddling,  re- 
heating, and  cupola  furnaces,  where  anthracite  is  burned ;  and  at 
cupola  furnaces,  where  coke  is  used  for  re-melting  pig  iron  in 
foundries.  Fig.  137  shows  a  section  of  a  common  fan.  The  two 
sides  of  the  case  are,  in  most  instances,  made  of  cast  iron,  and  held 
together  by  the  screw  bolts  «,  «,  #,  a.  These  bolts  reach  through 
both  sides,  and  their  length  is  therefore  equal  to  the  width  of  the 
machine,  which  varies  from  six  to  twenty  inches.  The  space  be- 
tween the  sides  is  occupied  by  a  strip  of  sheet  iron;  this  strip  de- 
termines the  width  of  the  machine,  and  reaches  all  around  the  fan, 
forming  the  circular  part  of  the  case.  The  wings  of  the  fan  marked 


408  MANUFACTURE   OF   IRON. 

5,  b,  b,  b,  are  of  sheet  iron ;  they  are  fastened  to  iron  arms  set  upon 
the  axis,  and  rotate  with  it,  and  they  occupy  a  different  position  in 

Fig.  137. 


Common  fan. 

different  fans.  Some  are  set  radially,  others  inclined  more  or  less 
tangentially.  Some  are  straight ;  others  have  a  slight  curvature. 
On  the  whole,  no  marked  difference  between  the  one  form  of  wings 
and  the  other  results,  so  far  as  effect  is  concerned,  if  no  blunders 
against  the  laws  of  mechanics  are  made.  The  fans  with  curved 
and  short  wings  do  not  make  so  much  noise  as  those  with  straight, 
radial,  and  long  wings.  The  opening  0,  which  receives  the  air, 
to  be  pressed  out  at  d,  must  be  of  greater  or  less  diameter,  according 
to  the  size  of  the  fan,  or  width  of  the  wings.  Broad  fans  re- 
quire such  an  opening  on  each  side.  Small  fans,  of  but  six  or  eight 
inches  in  width,  work  sufficiently  well  with  one  inlet.  The  diame- 
ter of  a  fan  is  seldom  more  than  three  feet,  and  from  various  reasons 
it  can  be  shown  that  a  larger  diameter  is  of  no  advantage.  The 
number  of  revolutions  of  the  axis,  or  the  speed  of  the  wings,  is 
very  seldom  less  than  700  per  minute;  this  speed  may  be  considered 
sufficient  for  the  blast  of  a  blacksmith's  forge,  and  small  furnaces. 
At  large  furnaces,  or  cupolas,  we  frequently  find  the  number  of 
revolutions  as  many  as  1800  per  minute.  The  motion  of  the  axis  is 
produced  by  means  of  a  leather  or  India  rubber  belt,  and  a  pulley 
of  from  four  to  six  inches  in  diameter. 

a.  Among  the  great  variety  of  forms  in  which  these  fans  have 
made  their  appearance,  one,  which  has  very  recently  been  issued 
in  Philadelphia,  is  certainly  worthy  of  the  particular  notice  of  the 


BLAST   MACHINES.  409 

manufacturer.  The  wings  of  this  fan  are  encased  in  a  separate 
box ;  a  wheel  is  thus  formed,  which  rotates  in  the  outer  box. — 
Fig.  138  shows  a  horizontal  section  through  the  axis.  The  wings  are 


Fig.  138. 


Improved  fan. 

thus  connected,  and  form  a  closed  wheel,  in  which  the  air  is  whirled 
round,  and  thrown  out  at  the  periphery.  The  inner  case,  which  re- 
volves with  the  wings,  is  to  be  fitted  as  closely  as  possible  to  the 
outer  case,  at  the  centre  near  a,  a,  a,  a\  for  no  packing  can,  in  this 
case,  be  applied,  and  there  is  a  liability  of  losing  blast,  if  the  two 
circles  do  not  fit  well.  This  fan  is  decidedly  better  than  the  com- 
mon fan,  and  is  fast  becoming  a  favorite  of  the  public. 

b.  As  the  building  of  this  apparatus  receives  much  attention 
in  our  machine  shops,  and  as  the  leading  principles  involved  in  its 
construction  are  very  little  known,  we  shall  designate  such  points 
as  may  be  deemed  of  great  importance  by  those  who  manufacture 
fans,  which  is  frequently  the  lot  of  the  iron  manufacturer  himself. 
The  outward  case  should  be  strong  and  heavy  ;  and  the  interior  ma- 
chinery, which  revolves,  as  light  as  possible.  For  this  reason,  it 
should  be  made  of  the  best  wrought  iron,  or,  what  is  preferable, 
of  steel.  Four  wings  produce  quite  as  much  effect  as  a  greater 
number.  It  is,  therefore,  useless  to  exceed  that  number.  The 
greatest  attention  must  be  paid  to  the  gudgeons  and  pans ;  it  is 
advisable  to  make  both  of  steel,  or,  better  still,  to  run  the  two  ends 
of  the  shaft  in  steel  points.  The  wings  are  to  be  exactly  at  equal 
distances,  and  of  equal  weight;  otherwise,  the  strongest  case  will 
be  shaken.  The  surface  of  each  of  the  wings  should  be  at  least 
twice  as  large  as  the  opening  of  the  nozzle  at  the  blowpipe. 

c.  The  pressure  of  theblast  from  a  fan  is  proportional  to  the  square 
of  the  speed  of  the  wings,  with  a  given  diameter  of  the  fan.  The 


410  MANUFACTURE  OF  IRON. 

pressure  gains  simply  in  the  ratio  of  the  diameter,  or  speed,  provided 
there  is  the  same  number  of  revolutions.  The  increase  of  speed  is 
in  the  ratio  of  the  increase  of  the  radius.  The  pressure  in  the  blast 
is  produced  by  centrifugal  force.  The  atoms  of  air,  after  being 
whirled  round  by  the  wings,  are  thrown  out  at  their  periphery  by  a 
force  equal  to  the  centrifugal  force  resulting  from  the  speed  of  the 

C2 
wings.     This  centrifugal  force  may  be  simply  expressed  by ; 

c  is  the  speed  in  feet  per  second ;  g  the  speed  of  gravitation  in  the 
first  second  ;  and  r  the  radius  of  the  fan.  According  to  this,  the 
effects  of  a  fan  ought  to  be  far  greater  than  they  actually  are ; 
therefore,  a  remarkable  loss  of  power  must  take  place  in  these  ma- 
chines. It  is  thus  very  clear  that  the  increase  of  diameter  aug- 
ments the  effect  of  the  machine  in  a  numerical  proportion,  while  an 
increase  of  revolutions  adds  to  the  effect  in  the  proportion  of  the 
square.  It  is  also  very  clear  that  an  increased  diameter  greatly 
increases  the  friction,  while  the  increase  of  speed  does  not  augment 
it  in  the  least.  The  friction,  in  these  machines,  is  the  greatest  ob- 
jection to  their  use;  therefore,  the  movable  parts  should  be  as  light 
as  possible.  Friction  increases  in  the  ratio  of  the  weight,  where 
the  materials  are  the  same,  but  not  with  an  augmentation  of  speed, 
at  least,  not  in  the  same  ratio.  From  practical  observation,  the 
following  formula  has  been  deduced  :  in  which  a  is  the  speed  of  the 
fan,  that  is  to  say,  it  represents  the  number  of  feet  which  the  wings 
make  in  a  second;  5,  the  surface  of  the  nozzle;  <?,  the  surface  of 
a  wing;  and  d,  the  velocity  of  the  escaping  blast.  This  formula 
we  conceive  to  be  the  proper  dimensions  of  a  fan  : — 

a 
d=  0,73  x~~ 


VII.  Receivers,  or  Regulators  of  Blast. 

Cylinder  blast  machines,  as  well  as  those  of  the  common  bellows 
form,  make  an  irregular  blast.  The  back  and  forward  motion  of  the 
piston,  which,  when  it  arrives  at  the  culminating  points,  ceases,  fora 
few  moments,  to  make  any  blast  at  all,  of  course  causes  an  inter- 
ruption of  supply  to  the  nozzles,  and  a  consequent  waving,  sinking, 
and  falling,  in  the  pressure  of  the  blast.  Uniformity  of  pressure  is  so 
important  an  object  at  the  blast  furnace,  that  too  much  attention 
cannot  be  paid  to  it ;  but  an  attention  commensurate  with  its  im- 


BLAST  MACHINES.  411 

portance  this  subject  has  never  received.  If  there  were  no  other 
argument  to  convince  the  skeptical ;  if  we  had  no  facts  to  prove  di- 
rectly the  great  value  of  a  uniform  pressure,  the  consideration  that 
different  pressures  are  necessary  in  blowing  different  furnaces 
ought  to  settle  the  question  conclusively.  We  know  that  one  kind 
of  charcoal  will  permit  a  pressure  of  but  half  a  pound,  while  another 
kind  requires  a  pressure  of  one  pound  and  more.  In  each  case, 
too  great  or  too  little  pressure  is  injurious.  Where  the  coal  is  of 
such  a  nature  as  to  require  but  three-quarters  of  a  pound  pres- 
sure, we  are  obliged  to  secure  that  amount.  If,  as  not  unfrequently 
happens,  we  make,  in  the  same  stroke  of  the  cylinder,  a  difference 
of  between  half  a  pound  and  a  pound,  we  destroy  fuel  uselessly, 
for  that  blast  which  is  below  three-quarters  of  a  pound,  as  well  as 
that  which  is  above  it,  is  only  a  waste. 

Regulators  of  blast,  commonly  called  receivers,  are  of  various 
forms.  Scientifically,  they  may  be  divided  into  three  classes: 
the  wet  receiver,  or  water  regulator ;  the  dry  receiver,  with  mov- 
able piston;  and  the  air  chamber,  of  constant  capacity.  The  wet 
receiver  is  not  to  be  recommended,  on  account  of  its  water.  Though 
this  water  should  be  covered  with  floating  oil,  or  other  matter,  as 
has  been  suggested,  the  receiver  would  not  be  adapted  for  use. 

a.  The  second  class,  or  the  dry  receiver  with  movable  piston,  is 
generally  employed,  in  blast  machines,  with  two  wooden  cylinders; 
and  in  some  machines,  with  iron  cylinders.     The  top  of  a  common 
blacksmith's  bellows  acts  on  the  same  principle,  and  belongs  to  this 
class.     This  receiver  is  more  perfect  than  the  first  kind,  but  it  is 
far  from  producing  a  uniform  pressure,  or  at  least  that  uniformity 
the  blast  furnace  requires.    For  forges,  such  receivers  answer  very 
well.     In  Fig.  132,  a  receiver  with  a  movable  piston  is  shown. 
Its  dimensions  should  be  very  nearly  those  of  one  of  the  cylinders. 
If  the  diameter  is  increased,  the  play  of  the  piston,  and  conse- 
quently the  resistance,  are  diminished;  the  latter  is  the  cause  of  the 
irregularities  in  the  blast.    If  the  dead  points,  caused  by  the  raising 
and  falling  of  the  piston,  could  be  obviated,  this  receiver  would 
be  useful;  but,  as  that  is  not  likely  ever  to  be  the  case,  there  is  little 
probability  that  this  apparatus  will  ever  become  a  favorite  among 
blast  furnace  owners. 

b.  The  air  chamber  of  constant  capacity  is  coming  more  and 
more  into  general  use ;  this  is  unquestionably  the  best  of  all  regu- 
lators.    Air  chambers  of  various  forms  hstve  been  tried :  that  the 
best  form  is  the  sheet  iron  cylinder  may  now  be  considered  a  settled 


412  MANUFACTURE   QF   IRON. 

question.  In  order  to  make  a  good,  uniform  blast,  this  receiver 
should  be  of  great  capacity;  if  sufficiently  large,  the  blast  is  per- 
fect. Partly  from  considerations  of  economy,  less  frequently  from 
those  of  expediency,  wooden,  stone,  or  brick  chambers  have  been 
used.  Vaults  cut  into  rock,  or  native  caves,  have  also  been  used 
as  blast  regulators.  All  these  experiments  have  furnished  no  in- 
ducements for  imitation,  because  the  difficulty  of  keeping  such  cham- 
bers air-tight  was  too  great  to  be  overcome.  Consequently,  most 
of  the  stone  and  wooden  chambers  have  been  abandoned,  and 
iron  ones  constructed.  At  the  present  time,  air  chambers  are  made 
of  sheet  iron  one-eighth  of  an  inch  thick,  and  of  greater  or  less 
capacity,  according  to  the  number  of  strokes  of  the  piston  of  the 
blast  machine,  and  the  capacity  of  the  cylinders. 

It  would  lead  us  too  far  to  enter  upon  a  thorough  investigation 
concerning  the  capacity  of  a  dry  receiver ;  but  we  shall  point  out 
such  facts  as  have  a  bearing  upon  the  question.  The  dimensions 
of  the  air  chamber  have,  in  no  respect,  any  relation  to  the  capacity 
of  the  blast  cylinder.  This  is  influenced  by  other  circumstances. 
The  irregularities  of  pressure  are  less  where  two  blast  cylinders 
are  working  than  where  but  one  is  employed ;  the  result  is  still 
better  where  three  are  used.  In  the  latter  case,  the  blast  is  gene- 
rally so  uniform  that  no  receiver  is  needed,  and  the  employment  of 
large  pipes  to  conduct  the  blast  to  the  furnace  is  all  that  is  re- 
quired. With  two  cylinders  and  double  stroke,  the  blast  ought  to 
be  nearly  uniform,  according  to  theoretical  calculations,  if  the 
weight  of  the  piston  is  counterbalanced.  This  is  generally  the 
case  at  the  Western  establishments,  and  is  exhibited  in  Fig.  133. 
Nevertheless,  in  practice  we  find  that  these  machines  answer  ex- 
cellently for  fineries  and  hard  coal,  while  they  are  insufficient  for 
soft  charcoal,  and  for  well-regulated  smelting  operations.  Blast 
machines,  with  two  double  stroke  cylinders,  but  without  beams 
and  counterbalance,  must  be  adjusted  by  direct  balance  weight, 
because  the  united  weight  of  the  two  pistons  is  too  great  even  for  a 
large  air  chamber.  To  set  the  cranks  opposite  each  other  in  such 
a  machine  is  not  advisable,  for  the  difference  in  pressure  is  so 
great  that  it  cannot  be  effectually  overcome  by  a  chamber.  Two 
cylinders  and  single  stroke  require  opposite  cranks.  A  blast  ma- 
chine with  a  single  cylinder  requires  the  largest  possible  air  cham- 
ber, particularly  where  a  waterwheel  or  an  expansion  steam-engine 
is  the  motive  power. 

The  dimensions  of  the  air  chamber  in  a  double  cylinder  machine 


BLAST  MACHINES.  413 

and  double  stroke  is  sufficiently  large  if  made  of  ten  times  the 
capacity  of  one  of  the  blast  cylinders.  With  one  cylinder,  or  two 
single  stroke  cylinders,  from  twenty  to  thirty  times  the  capacity  of 
the  cylinder  is  required.  If  large  air-pipes  are  employed,  and  if  the 
distance  from  the  blast  machine  to  the  furnace  is  considerable,  the 
capacity  of  the  pipes  may  be  taken  into  account.  Where  the  pipes 
are  narrow,  they  do  nothing  toward  equalizing  the  blast ;  on  the 
contrary,  they  cause  a  loss  in  power  by  friction. 

The  form  of  an  air-chamber  is  generally  that  of  the  cylinder,  like 
a  steam  boiler,  and  varies  from  four  to  eight  feet  in  diameter.  It 
sometimes  has  straight,  sometimes  convex  heads.  The  globular  form 
has,  in  some  places,  been  adopted,  but  we  do  not  think  that  this 
form  will  ever  be  used  extensively  in  this  part  of  the  world.  The 
thickness  or  strength  of  the  sheet  iron  for  an  air  chamber  is  made 
to  vary  according  to  the  pressure  of  the  blast ;  but,  as  the  strongest 
pressure  would  hardly  tear  iron  one-eighth  of  an  inch  thick,  and  as 
that  thickness  is  required  to  give  stability  to  the  form  of  the  cham- 
ber, the  question  is  one  of  slight  practical  interest.  An  air  cham- 
ber should  be  provided  with  a  safety-valve,  to  guard  against  acci- 
dents, as  well  as  with  a  manhole,  to  afford  an  opportunity  of  getting 
into  the  interior,  if  that  is  found  to  be  necessary.  The  air  chamber, 
unless  too  small,  is  the  best  of  all  regulators.  If  we  have  any 
doubt  in  relation  to  what  should  be  its  capacity,  it  is  always  better 
to  make  the  chamber  too  large  than  too  small. 

VIII.  Blast  Pipes. 

It  is  seldom  or  never  in  our  power  to  bring  the  blast  gene- 
rator close  to  the  tuyere.  Conductors  are  generally  required  to 
lead  the  blast  from  the  blast  machine  to  the  furnace.  Various 
forms  of  conductors  have  been  invented,  such  as  wooden  and  iron 
pipes,  of  a  round,  square,  and  polygonal  section;  but  at  present, 
scarcely  any  other  than  sheet  or  cast  iron  pipes  are  employed.  At 
forge  fires,  and  small  blast,  puddling,  and  re-heating  furnaces,  or  at 
those  places  where  but  little  pressure  is  required,  pipes  of  tin  plate 
are  used ;  but  where  stronger  pressure  is  needed,  as  at  charcoal  blast 
furnaces  working  hard  coal,  and  at  anthracite  and  coke  furnaces, 
pipes  of  sheet  iron  one-eighth  of  an  inch  thick,  or  of  cast  iron,  are 
used.  Cast  iron  would  be  preferable,  in  many  respects,  to  sheet 
iron  pipes,  but,  in  consequence  of  their  weight,  the  latter  are  coming 
more  and  more  into  general  use.  Sheet  iron  pipe  can  be  made  of 
almost  any  length,  and  it  has  an  advantage  in  the  small  number  of 


414  MANUFACTURE   OF  IRON. 

its  joints.  The  diameter  of  the  pipes  varies  according  to  the  amount 
of  air  which  is  to  pass  through  them.  Where  1000  cubic  feet  of  air 
per  minute  are  to  pass  through  one  of  medium  length,  the  diameter 
should  be  at  least  ten  inches.  Each  additional  1000  feet  should 
have  the  same  space,  so  that  4000  feet  per  minute  require  a 
diameter  of  twenty  inches.  If  the  distance  from  the  blast  machine 
to  the  furnace  is  more  than  100  feet,  the  diameter  of  the  pipe  is  to 
be  increased;  and  it  may  be  doubled  with  each  additional  100  feet, 
in  consequence  of  the  friction  of  the  air.  A  very  appreciable  loss 
of  blast  results  from  narrow  pipes. 

Cast  iron  pipes  require  many  joints;  they  are  liable  to  leak,  in 
consequence  of  the  destruction  of  the  cement  in  the  joints,  caused 
by  contraction  and  expansion;  this  is  particularly  the  case  in  long 
pipes.  For  cold  blast  pipes,  the  best  joint  we  can  us'e  is  the  leaden 
one  commonly  employed  in  light  gas  pipes.  Where  hot  air  is  to  be 
conducted,  as  in  the  use  of  hot  blast,  the  lead  is  liable  to  melt  by 
the  heat  of  the  air.  In  this  case,  the  joints  must  be  cemented  by 
a  fire  proof  material.  A  cement  which  resists  the  influence  of 
hot  air  is  composed  of  iron  filings,  turnings,  or  borings,  worked 
through  a  riddle  or  a  coarse  sieve,  to  make  it  uniform.  Seventy-five 
pounds  of  sifted  filings  are  to  be  mixed  with  one  pound  of  powdered 
sal  ammoniac  and  one  ounce  of  flowers  of  sulphur,  to  which  two 
pounds  of  clay  in  dry  powder  must  be  added.  The  whole  of  these 
ingredients  must  be  well  mixed  together,  and  kept  in  a  dry  place 
for  use.  Whenever  any  cement  is  wanted,  some  of  the  dry  and 
prepared  material  is  moistened,  and  used  immediately;  for,  as  it 
very  soon  oxidizes,  it  is  adapted  to  make  good  joints  only  when  it 
is  fresh.  A  few  days  are  required  to  harden  this  cement ;  but,  when 
thoroughly  indurated,  it  is  almost  as  durable  as  the  iron  itself.  If  pipes 
with  muffs  are  used,  which  are  preferable  to  those  with  flanches,  care 
must  be  taken  that  the  space  between  the  muff  and  the  pipe  is  not 
too  great;  one-quarter  of  an  inch  all  around  is  sufficient.  Where 
the  space  is  excessive,  the  expansion  of  the  cement,  occasioned  by 
the  oxidation  of  the  iron,  is  very  apt  to  break  the  muff.  Long,  straight 
pipes  are  very  liable  to  leak,  because,  from  their  length,  they  are 
stretched  by  a  high  heat.  By  reason  of  their  weight,  expansion  and 
contraction  break  the  cement  of  the  joints.  Such  pipes  should  be 
laid  upon  a  well-leveled  and  paved  foundation,  and  rested  upon 
rollers,  which  may  be  either  short  pieces  of  round  bar  iron,  or  short 
pieces  of  two  inch  cast  iron  pipes.  In  long  conductors,  the  expan- 
sion and  contraction  of  the  pipes  are  frequently  neutralized  by  sliding 


BLAST   MACHINES.  415 

muffs,  or  stuffing  boxes.  This  is  a  necessary  precaution  where  hot 
blast  is  to  be  conducted  a  considerable  distance.  Elbows  should  be 
avoided  as  much  as  possible  in  blast  pipes ;  and  if  necessitated  to 
use  them,  the  corner  should  be  turned  in  as  large  a  circle  as  pos- 
sible. The  loss  of  power  of  the  blast,  when  suddenly  turning  round 
a  corner,  is  very  great.  Acute  angles,  even  those  of  90°,  are,  if 
possible,  to  be  altogether  avoided.  The  best  location  of  blast  pipes, 
where  they  are  weak,  and  liable  to  break,  or  where  the  joints  are 
not  quite  safe,  is  above  ground.  For  well-constructed  and  pro- 
perly cemented  pipes,  the  best  situation  is  below  ground.  But  we 
ought  to  take  the  precaution  of  laying  them  in  well-constructed, 
spacious  channels,  walled  and  paved  with  brick  or  stone,  and 
covered  with  wood,  stone,  or  cast  iron  plate.  When  laid  in  the 
ground,  and  covered  with  earth,  they  are  very  liable  to  be  injured, 
and  seldom  answer  a  good  purpose.  It  is  better  to  lay  them  above 
ground  than  to  enclose  them  in  an  immovable  position.  Though 
corners  of  any  kind  are  to  be  avoided  in  blast  conductors,  we  must 
not,  therefore,  suppose  that  very  straight  pipes  are  the  best  form  we 
can  select.  A  gentle  bend  is  advantageous,  for  it  will  tend  to  pre- 
serve the  joints.  Various  plans  of  locating  the  blast  pipes  around  a 
blast  furnace  have  been  adopted.  In  some  instances,  we  see  the 
pipes  above  the  head;  in  others,  walled  in  the  pillars  ;  and  in  others, 
again,  below  the  bottom  stone  of  the  hearth.  The  latter  plan  is 
preferable ;  but,  unless  executed  with  due  care,  the  result  will  be 
unfavorable.  A  blast  pipe  thus  laid  should  be  entirely  free,  that  is, 
it  should  be  at  liberty  to  move  exactly  to  that  degree  which  the 
difference  of  temperature  to  which  it  is  exposed  inclines  it.  If 
this  precaution  is  taken,  we  experience  no  trouble  with  it.  An 
objection  has  been  raised  against  laying  the  pipes  in  this  manner, 
because,  in  some  cases,  hot  cinder  and  hot  iron  have  found  access 
into  the  channels  for  the  pipes.  But  such  accidents  cannot  be 
deemed  a  valid  objection.  They  can  be  avoided  by  a  judicious 
plan  of  laying  the  pipes,  and  by  proper  care  in  the  management  of 
the  furnace. 

a.  The  mouth-pieces  of  the  blast  pipes,  called  nozzles,  are  ta- 
pered sheet  iron  tubes,  varying  from  one  to  four  feet  in  length,  ac- 
cording to  locality,  and  the  purpose  which  they  serve.  At  one 
end,  they  are  as  wide  as  the  conducting  blast  pipe,  to  which  they 
are  joined ;  at  the  other  end,  they  are  as  wide  as  is  considered  neces- 
sary for  the  passage  of  the  blast.  These  nozzles  are  frequently 
divided  into  two  parts  ;  one  of  which  is  permanent,  and  the  other, 


416  MANUFACTURE   OF  IRON. 

generally  the  shorter,  movable.  This  facilitates  a  change  in  the 
dimensions  of  the  nozzles.  These  conical  pipes  are  either  welded 
or  soldered  with  copper,  for,  as  they  are  narrow,  rivets  will  obstruct 
the  blast,  and  make  it  exceedingly  noisy.  Where  cold  blast  is 
used,  the  nozzles  are  generally  connected  with  the  main  blast 
pipe  by  a  leather  bag.  This  bag  is  held  to  the  pipes  by  means  of 
an  iron  hoop.  This  hoop,  of  the  form  of  a  wristband,  is  tied  to 
its  place  by  a  screw,  which,  by  drawing  the  hoop  close  to  the  lea- 
ther, and  that  to  the  pipe,  makes  an  air-tight  joint.  Where  hot 
blast  is  employed,  leather  cannot  be  put  into  the  conducting  pipe. 
In  this  case,  everything  must  be  metal.  It  frequently  happens 
that  the  nozzles  are  to  be  temporarily  removed  ;  to  facilitate  this 
removal,  and  to  avoid  loss  of  time  as  much  as  possible,  a  joint  is 
required.  With  cold  blast,  the  motion  of  the  nozzle  from  one  place 
to  another  is  frequently  necessary,  and  more  or  less  dip  is  required  ; 
for  that  purpose,  the  leather-bag  connection  is  indispensable.  With 
hot  blast,  this  is  not  the  case,  and  therefore  movable  nozzles  are 
unnecessary. 

The  size  of  the  nozzle  is,  under  certain  circumstances,  a  matter 
of  great  importance,  and  deserves  more  attention  than  it  generally 
receives,  particularly  at  charcoal  blast  furnaces,  and  charcoal  forges. 
If  the  moving  power  of  the  blast  machine  is  limited,  then  it  is  the 
opening  of  the  nozzle  which  determines  the  pressure  of  the  blast. 
As  a  given  pressure  is  most  advantageous,  it  is  evident  that  the 
size  of  the  nozzle  must  have  considerable  influence  upon  the  smelting 
operations.  The  changing  of  nozzles  must  be  conducted  with  re- 
ference to  securing  a  permanent  pressure,  for  this  is  indispensable. 
The  amount  of  blast  may  be  increased  or  diminished.  The  dia- 
meter of  the  nozzle  is  of  course  subject  to  great  variations.  We 
employ  nozzles  of  one  inch  diameter  at  charcoal  forges;  from  one 
and  a  half  inch  to  two  and  a  half  inches  at  charcoal  furnaces  ;  and 
from  three  to  four  inches  diameter  at  coke  and  anthracite  furnaces. 
Where  other  things  are  equal,  the  nozzles  for  hot  blast  should  be 
larger  than  those  for  cold  blast.  The  form  or  taper  of  the  nozzle  at 
the  point  is  a  matter  of  considerable  consequence  ;  the  greater  the 
taper,  that  is,  the  larger  the  angle  of  convergence  towards  the  point, 
the  more  the  blast  spreads  into  the  furnace.  Its  results  are  similar 
to  those  of  a  weaker  blast.  An  application  of  this  principle  is  made 
at  the  charcoal  forge,  and,  in  some  places  of  the  Old  World,  at  the 
blast  furnace,  by  employing  two  nozzles,  which  blow  in  such  direc- 
tions as  to  spread  the  blast  in  a  greater  degree  among  the  hot  coal. 


BLAST  MACHINES.  417 

Stronger  blast  may  be  thus  applied  to  soft  coal,  in  which  case  it  is 
advantageous.  The  more  cylindrical  the  form  of  the  nozzle,  the 
greater  the  degree  in  which  the  blast  will  be  kept  together  in 
the  furnace.  This  form  improves  the  pressure  of  the  blast.  Simi- 
lar results  take  place  where  only  the  extreme  end  of  the  nozzle 
is  cylindrical  to  a  length  equal  to  the  diameter  of  the  opening. 
That  is,  a  three  inch  nozzle  requires  a  cylindrical  nose  three  inches 
long  to  form  a  compact  column  of  blast ;  and  a  two  inch  nozzle  re- 
quires a  nose  two  inches  in  length.  Cylindrical  nozzles  are  prefer- 
able for  hard  coal;  tapered  nozzles  for  soft  coal,  charcoal  forges,  and 
fineries.  Long  and  narrow  tubes  occasion  much  friction ;  therefore, 
it  is  advantageous  to  make  the  nozzles  as  short  as  possible.  The 
current  of  blast  is  moulded  at  the  very  extreme  end  of  the  nozzle. 

IX.   Tuyeres. 

Much  doubt  and  uncertainty  exist  in  relation  to  tuyeres,  and 
therefore  we  shall  make  them  the  subject  of  special  investigation. 
Before  puddling  was  so  generally  introduced  as  at  present,  the  shape 
and  position  of  the  tuyere  at  a  blast  furnace  received  considerable 
attention  ;  but,  since  the  quality  of  pig  iron  has  been  sought  for  with 
but  little  anxiety,  the  tuyere  ceases  to  be  of  much  importance. 
The  chief  purpose  of  the  metallic  tuyere  is  the  preservation  of  the 
fire-proof  hearthstones  ;  the  direction  and  form  of  the  blast  are  of 
minor  importance.  This  protection  is  accomplished,  in  some  mea- 
sure, by  making  a  coating  of  fire-clay  in  the  tuyere  hole,  which 
is  cut  in  the  hearthstones.  By  this  means,  constant  attendance, 
and  repeated  renewal  with  clay,  will  enable  us  to  keep  the  tuyere 
narrow.  No  tuyere,  whether  of  clay  or  metal,  should  ever  be  wider 
than  the  nozzle.  Where  one  of  the  former  kind  exceeds  the  width 
of  the  nozzle,  it  burns  away,  and  the  hearth  is  exposed  to  destruc- 
tion. The  preservation  of  the  original  dimensions  of  the  hearth  is  the 
main  object  which  the  manager  of  a  furnace  seeks  to  secure ;  and, 
as  the  clay  tuyere  does  not  effect  this  object,  tuyeres  made  of  cop- 
per or  cast  iron  have  been  substituted  in  its  place.  These  reach 
farther  into  the  furnace  than  the  clay  tuyere,  and,  therefore,  as  it  is 
decidedly  of  advantage  that  the  blast  should  be  driven  as  far  as 
possible  into  the  centre  of  the  hearth,  they  are  much  preferable  to 
the  latter.  Wrought  iron  tuyeres  are  liable  to  burn.  The  iron,  in 
consequence  of  its  purity,  oxidizes,  and  forms  with  the  clay  around 
it  a  very  fusible  silicate,  which  is  precipitated  into  the  furnace. 
Gray  is  preferable  to  white  cast  iron,  and  also  to  wrought  iron ;  the 
27 


418  MANUFACTURE   OF  IRON. 

carbon  and  impurities  it  contains  protects  it  against  oxidation  and 
destruction.  Copper  is  the  best  metal  for  tuyeres  ;  it  is  a  good  con- 
ductor of  heat,  and  is  kept  cool  by  the  blast  more  easily  than  iron. 
Its  silicates  also  are  infusible.  If  copper  oxidizes,  and  forms  a  sili- 
cate, the  latter  will  protect  it.  The  advantages  derived  from  the 
copper  tuyere  have,  in  Europe,  been  acknowledged  for  more  than 
a  century ;  still,  the  charcoal  furnaces  in  this  country,  at  which  cold 
blast  is  employed,  are  generally  blown  by  clay  tuyeres,  the  result 
of  which  is  the  waste  of  a  great  deal  of  coal,  and  the  production  of 
inferior  iron.  We  do  not  recommend  the  application  of  the  copper 
tuyere,  for  the  water  tuyere  is  preferable ;  but  mention  the  above 
fact  as  a  curiosity — as,  in  fact,  one  of  those  rare  cases  in  which  our 
citizens  do  not  make  the  best  use  of  the  means  at  their  disposal.  The 
copper  tuyere  is  protected  against  the  heat  of  the  furnace  by  the 
cold  blast,  which  touches  it,  and  cools  it ;  for  this  reason,  the  tuyere 
should  not  be  wider  than  the  nozzle.  In  this  point  of  view,  we  may 
regard  the  tuyere  as  a  prolongation  of  the  nozzle,  in  which  case,  of 
course,  it  is  governed  by  the  rules  applicable  to  the  latter.  So  long 
as  pig  iron  is  to  be  made  for  the  charcoal  forge,  the  desire  to  make 
white  plate  iron  in  the  blast  furnace  will  exist.  It  is  very  difficult, 
almost  impossible,  to  keep  a  blast  furnace  constantly  running  upon 
a  certain  kind  of  iron ;  therefore,  the  difference  which  the  quality 
of  that  in  the  furnace  exhibits,  is  modified  to  a  more  or  less  general 
standard  by  means  of  the  position  of  the  tuyere,  such  as  its  direc- 
tion and  inclination.  Very  skillful  management  is  required,  in  many 
instances,  to  produce  the  desired  effect.  In  some  parts  of  Europe, 
where  cold  blast  iron  for  the  forge  is  manufactured,  the  copper  tuy- 
ere is  yet  in  use ;  but  where  pig  iron  for  puddling  is  made,  or  hot 
blast  employed,  the  tuyere  will  not  require  such  close  attention.  In 
this  country,  we  can  scarcely  appreciate  the  niceties  involved  in  ad- 
justing the  tuyere,  not  even  at  the  forge  fires  ;  but  this  adjustment 
is  unaccompanied  with  any  practical  convenience,  for  the  trouble 
it  requires  is  never  compensated.  The  advantages  which  arise  from 
a  scrupulous  attention  to  the  tuyere  are,  at  best,  very  small ;  and 
such  attention  would,  under  the  conditions  which  exist  in  this  coun- 
try, especially  the  high  price  of  labor,  result  in  loss  instead  of  gain, 
a.  At  cold  blast  furnaces,  in  this  country,  clay  or  cast  iron 
tuyeres,  principally  the  former,  are  generally  employed.  Water 
tuyeres  are  in  use  at  forges,  fineries,  hot  blast,  and  at  some  cold 
blast  furnaces.  A  common  tuyere  for  the  Catalan  forge,  the  char- 
coal forge,  finery,  and  charcoal  blast  furnaces,  is  made  of  boiler- 


BLAST   MACHINES. 


419 


plate;  it  is  represented  by  Fig.  139.     The  top  part  is  hollow,  while 
the  bottom  part,  which  is  generally  flat,  as  shown  at  c,  is  solid.    A 


Section  and  view  of  a  water  tuyere  with  flat  bottom. 

water  pipe  of  one-half  inch  bore  conducts  a  current  of  cold  water 
through  the  hollow  top;  this  preserves  the  tuyere,  and  protects  it 
against  burning.  The  bottom  is  made  flat,  so  as  to  serve  as  a  sup- 
port to  the  nozzle  ;  we  are  thus  enabled  to  move  the  latter  to  those 
places  where  it  is  most  needed.  At  blast  furnaces  and  fineries, 
this  precaution  is  not  of  much  use,  for  the  nozzle  remains  at  the 
place  where  it  is  fixed ;  but  at  forges  it  must  be  movable.  Both 
of  the  water  pipes  are,  in  most  cases,  at  the  top ;  this  arrangement 
can  scarcely  be  considered  so  advantageous  as  that  in  which  one 
pipe,  or  the  entrance  of  the  water,  is  nearer  the  bottom,  and  the 
other  pipe,  or  the  outflow,  at  the  top. 

b.  Tuyeres  for  anthracite,  coke,  and  most  of  the  charcoal  fur- 
naces, are  perfectly  round,  and  made  of  boiler-plate  ;  seldom  of 
copper  or  cast  iron.  Fig.  140  shows  a  round  water  tuyere ;  this 
may  be  two  inches  wide  at  the  narrowest  point,  as  at  charcoal  fur- 
naces, or  from  four  to  four  and  a  half  inches,  as  is  the  case  at 
anthracite  furnaces.  The  taper  of  the  tuyere  does  not  affect  the 

Fig.  140. 


Round  water  tuyere. 

furnace,  and,  for  all  the  evil  this  tapering  occasions,  it  may  be  a 
perfect  cylinder.  In  using  hot  blast,  it  makes  no  difference  how 
the  air  is  conducted  into  the  furnace,  provided  the  tuyere  is  kept 


420  MANUFACTURE   OF   IRON. 

open,  and  bright,  which  is  all  that  is  necessary.  The  nozzle  is  laid 
into  the  tuyere — how  far  it  reaches  into  it,  is  a  matter  of  no  conse- 
quence— and  the  space  between  them  filled  up  with  clay.  At  a  cold 
blast  furnace,  it  requires  some  attention  not  to  push  the  nozzle  too 
far  in,  or  to  draw  it  too  far  back.  The  water  pipes,  marked  a  and  5, 
are  of  lead,  three-fourths  of  an  inch,  seldom  one  inch,  bore;  one  on 
the  lower,  and  the  other  on  the  top  part  of  the  brim.  The  lower 
pipe  conducts  the  water  to  the  tuyere,  and  the  upper  conducts  it 
from  the  tuyere.  The  former  is,  in  many  cases,  pushed  as  far 
as  possible  into  the  interior  of  the  tuyere,  to  bring  the  cold  water 
into  the  furnace;  the  water  is  thus  applied  where  the  heat  is 
greatest.  A  constant,  uninterrupted  supply  of  water  is  necessary 
to  prevent  the  melting  of  the  tuyere.  The  water  must  be  pure; 
else  it  will  leave  a  sediment  in  the  tuyere  which  is  sure  to  cause  its 
destruction.  There  must,  also,  be  a  sufficient  amount  of  cold  water ; 
for,  if  the  formation  of  steam  is  going  on  in  the  interior  of  the 
tuyere,  the  latter  is  sure  to  be  burned.  Copper  and  brass  last  longer 
than  iron;  but  if  iron  tuyeres  are  well  made,  and  soldered  with 
copper,  and  if  there  is  no  lack  of  water,  they  may  last  a  long 
time.  Where  there  is  deficiency  of  water,  or  where  there  are 
sediments  in  the  interior  of  a  tuyere,  a  few  hours'  heat  will  destroy 
it.  If  we  find  that  the  tuyeres  do  not  wear  well,  our  attention  must 
be  directed  to  the  water;  if  nothing  appears  wrong,  the  application 
of  larger  pipes,  or  higher  hydrostatic  pressure,  will  then  remedy  the 
evil.  Water  tuyeres  are  generally  from  ten  to  twenty  inches  long ; 
tuyeres  that  are  too  short  are  liable  to  be  burnt,  by  the  fire  working 
around  them,  because  there  is  not  sufficient  room  to  keep  it  closed  up. 
Another  disadvantage  of  such  tuyeres  is,  that  their  want  of  length 
prevents  them  from  being  pushed  into  the  hearth;  but  length  is  neces- 
sary when  the  hearth  is  burned  out,  and  when  we  wish  to  carry  the 
blast  further  into  the  interior.  The  external  size  of  the  tuyere  is 
a  matter  which  requires  attention  in  its  construction.  The  total 
surface  determines  the  amount  of  water  which  is  necessary  to  keep 
it  cool.  The  larger  the  surface,  particularly  the  diameter,  the 
greater  the  amount  of  water  necessary,  and  of  course  the  greater 
the  danger  of  burning.  A  tuyere  is  seldom  more  than  four  inches 
in  diameter  inside  ;  and  we  frequently  see  tuyeres  whose  diameter 
outside  is  twelve,  and  even  more  inches.  In  this,  there  is  some- 
thing wrong,  for  with  the  increase  of  the  diameter  is  the  augmen- 
tation of  the  danger. 

Tuyeres  may  be  considered  a  prolongation  of  the  nozzle  or  the 


BLAST  MACHINES.  421 

blast  pipe,  and  disconnected  from  it  merely  for  the  sake  of  preser- 
vation, and  of  more  convenient  access  to  the  interior  of  the  furnace. 
Cold  blast  should  taper  more  than  hot  blast  tuyeres,  because  the  for- 
mer clinker  in  a  greater  degree,  and  require  cleaning  more  frequently 
than  the  latter.  The  more  acute  the  angle  of  the  tuyere,  the  colder 
it  works;  the  more  tapered  it  is,  the  hotter  it  works.  These  obser- 
vations are  of  practical  importance.  In  most  cases,  we  want  the 
blast  as  far  in  the  interior  of  the  furnace  as  possible,  because  fuel 
is  thus  saved,  better  iron  is  produced,  and  the  hearth  protected. 
There  is  some  difficulty  in  giving  cold  blast  tuyeres  a  slight  taper, 
because  they,  should  be  very  wide  outside ;  but  this  difficulty  can 
be  overcome  by  making  the  interior  of  the  tuyere  curved.  If  its 
extreme  end,  as  far  back  as  the  diameter  of  the  mouth,  is  cylin- 
drical, the  same  purpose  is  accomplished  as  though  the  whole  tuyere 
was  a  cylinder.  If  the  tuyere  is  too  much  tapered,  which  is  shown 
by  its  working  too  hot,  we  lessen  the  evil,  in  some  measure,  by 
pushing  the  nozzle  further  into  the  furnace.  This  is  but  a  tempo- 
rary, not  a  radical,  remedy ;  tuyeres  of  the  proper  form  must  be 
substituted.  If  the  tuyere  works  too  cold,  that  is,  sets  on  too  much 
cold  cinder,  our  only  resource  is  scrupulously  to  keep  it  clean,  and 
to  replace  it  as  soon  as  possible  by  a  more  tapering  tuyere,  or  a 
more  obtuse  cone.  From  these  considerations,  it  is  evident  that  dif- 
ferent kinds  of  ore  require  a  tuyere  of  different  taper ;  for  the  exact 
degree  of  this  taper,  no  general  rule  can  be  given.  Experience  must, 
in  this  instance,  be  our  only  guide.  This  will  appear  more  evident, 
if  we  consider  that  the  kind  of  fuel  and  the  pressure  of  the  blast 
must  also  be  taken  into  consideration  when  we  construct  a  tuyere. 
Calcareous  ere,  as  well  as  the  pig  iron  made  from  it,  works  natu- 
rally hot  at  the  tuyere;  consequently,  we  employ  acute  tuyeres: 
these  serve  to  drive  the  blast  far  into  the  furnace,  by  which  means 
they  will  be  kept  cool.  This  result  can  be  effected  by  a  water 
tuyere.  Clay  ores — which  work  naturally  cold  at  the  tuyere — work 
better  with  a  tuyere  that  is  tapered,  in  which  case,  a  water  tuyere  is 
not  so  favorable.  These  considerations  have  a  special  bearing  upon 
the  working  of  furnaces  and  forges,  and  are  of  an  entirely  practical 
nature.  For  this  reason,  the  management  of  the  furnace  or  forge 
is  accompanied  with  such  different  results.  It  is  evident  that  the 
modification  of  a  tuyere  cannot,  at  times,  be  so  quickly  accomplished 
as  we  desire.  Months,  and  even  years,  are  often  consumed,  before 
the  required  form  can  be  determined;  in  many  cases,  this  form  is 
never  arrived  at.  The  shape  of  the  tuyere  is,  therefore,  a  matter 
which,  at  blast  furnaces,  generally  depends  on  the  decision  of  the 


422  MANUFACTURE   OF   IRON. 

keeper  or  founder ;  and  as  the  clay  tuyere  may  be  altered  very  con- 
veniently, this  may  be  assigned  as  one  of  the  reasons  why  so  many 
tuyeres  of  this  kind  are  in  use.  The  whole  matter  is  divested  of  its 
mystery,  if  we  reflect  that  an  obtuse  tuyere  tends  to  work  warm, 
and  an  acute  tuyere  to  work  cold.  The  latter  is  more  advan- 
tageous than  the  former,  as  respects  both  the  quality  and  quan- 
tity of  work ;  but  it  is  more  difficult  to  manage.  But,  as  the  form 
of  the  nozzle,  as  well  as  that  of  a  metal  tuyere,  is  permanent,  the 
latter  maybe  a  dry  or  water  tuyere;  and  as  the  advantage  of  either 
shape  can  be  arrived  at,  in  a  more  or  less  perfect  manner,  by  push- 
ing in  or  drawing  back  the  nozzle,  no  solid  objection  exists  against 
metal  tuyeres.  In  these  cases,  there  ought  to  be  a  difference  be- 
tween the  form  of  the  nozzle  and  that  of  the  tuyere.  An  obtuse 
nozzle  should  work  with  an  acute  tuyere ;  a  slightly  tapered  nozzle 
with  a  greatly  tapered  tuyere.  The  latter  form  is  generally  pre- 
ferred, on  account  of  the  facilities  it  offers  for  cleaning  the  tuyere. 

In  applying  hot  blast,  the  form  of  the  tuyere  and  the  nozzle  is  a 
matter  of  indifference;  still,  while  constructing  them,  it  will  do  no 
harm  to  take  the  above  rules  into  consideration.  The  advantages 
of  hot  blast  are  sometimes  doubtful.  It  may  be  as  well  to  unite,  by 
means  of  perfect  forms  of  apparatus,  all  the  advantages  deriva- 
ble from  cold  blast ;  we  can  thus  regain  what  is  lost  in  quantity  by 
its  employment. 

In  Chapter  III.,  we  have  spoken  of  the  relative  advantages  of 
a  greater  or  less  number  of  tuyeres  in  the  same  apparatus.  In 
forge  fires,  we  generally  observe  but  one  tuyere  and  two  nozzles,  of 
the  course  of  whose  application  there  can  be  no  doubt.  At  refinery 
fires,  we  often  see  the  tuyeres  all  on  one  ,side ;  at  other  places,  on 
opposite  sides :  in  one  tuyere  we  see  two  nozzles,  and  in  others 
but  one.  All  these  differences  are  the  result  of  local  causes,  ori- 
ginating in  the  form  of  the  apparatus,  the  quality  of  the  iron  and 
fuel,  the  pressure  of  the  blast,  and  the  qualification  of  the  workmen ; 
these  causes  will  be  clearly  understood  from  our  previous  investiga- 
tions. The  number  of  the  tuyeres,  and  their  position  in  the  blast 
furnace,  are  of  sufficient  importance  to  deserve  our  attention.  In 
the  same  chapter,  we  remarked  that,  in  using  cold  blast,  we  should 
employ  as  few,  and  in  using  hot  blast,  as  many,  tuyeres  as  possible. 
Cold  blast  tuyeres  are  naturally  troublesome ;  they  are  apt  to  become 
black;  they  require  constant  attention,  as  well  in  moving  the  nozzle 
as  in  patching  the  tuyere  with  clay ;  they  tend  to  produce  white  iron, 
and  they  cool  the  lower  parts  of  the  hearth.  For  these  reasons,  we 
would  reduce  the  number  of  these  tuyeres  as  much  as  possible. 


BLAST  MACHINES.  423 

The  hot  blast  tuyere  works  very  hot ;  occasions  but  little  trouble  ; 
is  too  much  inclined  to  produce  gray  iron ;  and  tends  to  reduce 
silex,  and  consequently  to  produce  a  poor  quality  of  iron.  There- 
fore, we  recommend  the  use  of  as  manjfc  hot  blast  tuyeres  as  con- 
veniently can  be  employed.  The  position  of  the  tuyeres  is  most 
favorable  when  placed  on  both  sides  of  the  hearth.  The  timp  is 
that  part  of  the  hearth  which  is  first  burnt  out ;  and  if  the  tuyere 
is  in  the  back  part  of  the  hearth,  the  distance  from  it  to  the  oppo- 
site timp  is  unnecessarily  increased. 

X.  Valves. 

Valves  are  essential  in  blast  conducting  pipes :  first,  for  shutting 
up  the  blast  entirely ;  secondly,  for  diminishing  and  increasing  it 
at  pleasure.  The  first  kind  is  needed  where  the  blast  is  generated, 
for  various  purposes,  by  the  same  blast  machine.  The  valves  in 
use  are  the  sliding,  the  conical,  and  the  trundle.  The  first  two  are 
at  present  but  little  employed.  If  well  made,  the  latter  kind  of 
valve  is  very  useful.  Fig.  141  shows  a  longitudinal  section  of  a 
part  of  a  pipe  and  a  valve :  a  is  a  section  through  the  axis  of  the 
valve,  and  b  a  view  of  the  valve  and  a  section  of  the  pipe.  The 
axis  runs  through  the  pipe  at  both  ends.  At  one  end  it  has  a 
handle,  and,  in  many  instances,  a  graded  scale,  which  indicates  the 
amount  of  air  which  passes  through  the  valve,  or,  in  other  words,  it 
shows  the  opening  of  the  valve.  At  each  tuyere  or  nozzle,  a  valve 

Fig.  141. 


Trundle- valve. 

is  required,  which  serves  either  to  shut  off  the  blast  entirely,  or  to 
regulate  the  passage  of  whatever  amount  is  needed.  At  the  nozzle 
valve,  a  scale  is  very  useful,  partly  for  the  purpose  of  adjusting  the 
blast,  and  partly  for  that  of  fastening  the  handle  of  the  valve,  and 
keeping  it  in  a  certain  position. 

The  laws  which  govern  the  construction  of  blast  pipes,  valves, 
and  tuyeres,  are,  summarily,  as  follows :  The  interior  of  the  blast 
conductors  should  be  as  smooth  as  possible,  for  an  uneven  surface 
causes  great  friction.  The  friction  of  the  air  is  proportional  to  the 
length  of  the  pipe,  and  to  the  density  of  the  air  which  passes  through 


424  MANUFACTURE    OF  IRON. 

it.  It  is  proportional  to  the  square  of  the  speed  of  the  air,  and  the 
reverse  of  the  square  of  the  diameter  of  the  pipe.  Obstructions 
caused  by  short  bends  in  the  pipes  are  inversely  proportional  to  the 
angle  of  the  bend,  and  are  governed  by  the  laws  of  hydrostatics. 
Sudden  contractions  and  expansions  of  the  pipe  occasion  a  whirling 
disturbance  in  the  current  of  the  air — a  loss  of  power,  or,  what  is 
the  same,  of  blast. 

XI.  Manometer. 

The  pressure  of  blast  necessary  for  different  operations  is  an 
interesting  question,  and  one  undoubtedly  of  practical  importance. 
If  we  know  what  is  required,  we  ought  to  be  enabled  to  judge  to 
what  extent  we  can  succeed  in  accomplishing  what  we  propose  to 
ourselves.  To  measure  the  pressure  of  the  blast,  the  surface  of  the 
safety-valve  is  generally  resorted  to — that  is,  observing  the  whole 
weight  of  the  valve,  and  the  surface  of  opening  it  covers.  This  is 
a  very  imperfect  way  of  coming  to  a  knowledge  of  its  true  value;  for, 
if  the  plate  of  the  valve  is  much  larger  than  the  opening  it  covers, 
the  real  pressure  of  the  blast  may  be  but  half  of  that  which  the 
safety-valve  indicates.  The  real,  active  pressure  must  be  found  at 
the  nozzle  ;  and  if  we  reflect  upon  the  impediments  which  the  blast 
receives  in  its  passage  to  the  tuyere,  we  shall  have  no  doubt  as  to 
the  necessity  of  measuring  the  pressure  of  blast  at  that  point. 
The  most  simple  form  of  a  manometer,  or  measurer  of  blast,  is 
represented  by  Fig.  142 ;  it  is  a  glass  tube  of  the  size  of  a  baro- 
meter tube,  bent  as  shown  in  the  figure,  a  is  a  cork  stopper,  which 
is  pushed  upon  the  tube  ;  this  fits  in  a  hole  bored  into  the  blast  pipe 

as  near  the  nozzle  as  practicable.  Such 
a  manometer  is  easily  made.  A  piece  of 
glass  tube  can  be  obtained  from  almost 
any  glassware  store,  the  length  of  which, 
for  a  charcoal  furnace,  should  be  twelve 
inches,  and  for  an  anthracite  furnace, 
twenty-four  inches.  Such  a  glass  tube 
can  be  heated  to  redness  in  a  strong 
flame  of  alcohol,  just  at  its  centre,  and 
the  two  ends  bent  round  to  form  a  si- 
phon. The  one  leg  may  be  heated  to 
form  the  protection  for  the  stopper.  This 
tube  is  partly  filled  with  mercury,  which 
"Manometer.  should  reach  sufficiently  high  above  the 

lower  bend,  in   inches,  to    equalize  the 


BLAST  MACHINES.  425 

pressure  of  the  blast  in  pounds.  An  additional  inch  should  be 
added  to  keep  the  mercury  always  in  both  legs  of  the  tube.  If  the 
bend  at  a  is  connected  with  the  blast  pipe,  and  the  compressed  air 
is  working  upon  the  mercury,  the  latter  will  be  pressed  down  in  a, 
and  rise  in  d  proportionally  to  the  density  of  the  blast,  or,  as  it  may 
more  clearly  be  expressed,  proportionally  to  the  difference  between 
the  density  of  the  atmosphere  and  the  density  of  the  blast.  The 
difference  in  inches  in  the  height  of  the  mercury  between  a  and  d 
amounts  very  nearly  to  the  pressure  of  the  blast  in  pounds,  if  we 
divide  this  difference  by  2.  From  this,  it  is  evident  that,  as  the 
mercury  sinks  as  much  in  a  as  it  rises  in  d,  its  height  in  d,  above 
the  level  a  d,  which  is  the  line  of  rest  of  the  mercury,  is,  measured 
in  inches,  very  nearly  equal  to  a  pound  of  pressure  of  the  blast  to 
each  square  inch.  For  practical  purposes,  this  simple  instrument 
may,  by  calling  the  height  above  a  d,  in  inches,  pounds  of  pressure, 
be  deemed  quite  sufficient.  A  division  of  inches,  and  twelfths  of 
inches,  may  be  cut  into  the  glass.  The  mercury  should  always  be 
kept  as  high  as  a  d.  A  perfectly  plumb  or  perpendicular  direction 
of  the  leg  d  is  indispensable,  if  we  wish  to  obtain  accurate  results. 
Where  hot  blast  is  used,  the  mercury  would  evaporate,  by  coming 
in  contact  with  it.  This  evaporation  may  be  prevented  by  put- 
ting the  manometer  to  the  end  of  a  lead  or  iron  pipe  of  an  inch  or 
less  bore,  and  by  putting  this  pipe,  which  conducts  the  blast  from 
the  main  pipe  to  the  manometer,  into  a  trough  of  cold  water ;  the 
hot  air  will  thus  be  cooled  before  it  reaches  the  mercury. 

Measurement  of  the  pressure  or  density  of  the  blast,  whether  for 
our  own  observations,  or  for  comparison  with  those  made  at  other 
establishments,  is  almost  indispensable.  It  affords  an  opportunity 
both  for  observing  imperfections  in  our  own  blast  machines,  and  for 
obviating  them.  It  shows  the  difference  which  exists  between  the 
densities  of  the  blast  of  different  establishments,  which  difference 
escapes  common  observation.  Above  all  things,  it  draws  our  atten- 
tion to  the  oscillations,  or  difference  of  density,  caused  by  the  ma- 
chinery, and  will  assist  us  in  correcting  them.  The  density  of  the 
blast  is  no  absolute  measure,  whether  taken  at  the  manometer  or 
by  any  other  means.  This  density  is  the  difference  between  the 
density  of  the  atmosphere  and  the  pressure  in  the  blast  pipe.  A 
given  power  at  the  blast  machine  will  throw  a  greater  amount  of 
blast  into  the  furnace  when  the  mercury  in  the  barometer  is  low, 
than  when  it  is  high. 


426  MANUFACTURE    OF  IRON. 

XII.  General  Remarks  on  Blast  Machines,  <$-c. 
It  is  generally  admitted  that  no  economy  should  be  exhibited 
which,  in  any  respect,  interferes  with  the  quality  of  machinery.  If 
this  is  true  in  relation  to  every  department  of  iron  manufacture,  it 
is  particularly  true  with  reference  to  the  blast  machines  connected 
with  the  blast  furnace.  No  expense  ought  to  be  considered,  where 
the  matter  which  concerns  us  is  a  blast  machine.  Though  permit- 
ted to  economize  to  an  extent  which  would  injure  the  utility  of  any 
other  apparatus,  yet  so  great  is  the  importance  of  the  blast  machine, 
that  our  success  is  commensurate  with  the  manner  in  which  it 
works.  The  pressure  of  the  blast  ought  to  be  at  all  times  perfectly 
within  the  power  of  the  manager  of  the  furnace.  For  this  purpose, 
a  well-constructed  machine,  and  a  surplus  of  power,  are  indispens- 
able. The  oscillations  of  the  pressure  ought  to  be  as  slight  as  pos- 
sible. It  is  almost  impossible  to  make  a  uniform  blast  without  a 
receiver ;  for  this  reason,  it  is  advisable  to  employ  a  regulator  at 
every  blast  machine.  The  iron  cylinder  machine  is  undoubtedly 
preferable  to  all  other  blast  machines.  Anthracite,  coke,  and  hard 
charcoal  furnaces  cannot  be  carried  on  to  advantage  without  iron 
bellows.  In  wooden  cylinders,  a  pressure  as  high  as  five-eighths 
or  three-quarters  of  a  pound  may  be  obtained ;  this  is  sufficient  for 
forge  fires,  and  blast  furnaces  where  pine,  or  ill-charred  leaf-wood 
charcoal  is  employed.  Hard,  sound  charcoal,  anthracite,  and  coke 
require  a  greater  degree  of  pressure.  The  best  fans  seldom  produce 
a  pressure  of  a  quarter  of  a  pound;  still,  a  well-constructed  fan  may 
blow  a  Catalan  or  a  German  forge. 

a.  The  effect  of  iron  cylinder  blast  machines,  compared  with 
that  of  the  motive  power  applied,  is  from  60  to  65  per  cent. ;  of 
wooden  cylinders,  from  50  to  55 ;  of  the  blacksmith's  bellows,  and 
wooden  bellows  of  similar  construction,  from  30  to  40;  and  of  all 
the  fancy  machines  scarcely  from  15  to  20  per  cent.     The  Cag- 
niardelle,  or  screw  bellows,  is,  in  this  respect,  superior  to  all,  for 
its  effect  amounts  to  from  90  to  95  per  cent,  of  the  power  applied. 

b.  The  location  of  the  blast  machine  should  be  as  near  to  the  fur- 
nace as  possible,  with  the  object  of  avoiding  long  blast  conductors. 
Too  close  proximity  to  the  furnace  is  as  bad  as  too  great  a  distance 
from  it,  for  the  air  around  the  furnace  is  always  warm,  and  con- 
sequently contains  considerable  moisture.     A  cool,  dry  place,  to 
which  no  moisture  has  access,  and  which  is  free  from  sand  and  dust, 
is,  of  all  locations,  the  best.     The  air  contiguous  to  a  furnace  is 


BLAST   MACHINES.  427 

always  impregnated  with  sand  or  dust,  which  will  be  drawn  into 
the  blast  cylinders,  and  injure  the  machinery.  We  ought  to  be 
very  cautious  in  selecting  the  locality  of  fans ;  otherwise,  a  con- 
siderable loss  of  power  ensues.  The  pressure,  or  blast,  in  a  fan 
is  produced  by  centrifugal  force;  and  as  the  specific  gravity  of  the 
air  augments,  in  some  measure,  the  effect  produced,  it  is  evident 
that  the  air  passing  through  it  ought  to  be  as  cold,  or  heavy,  as  pos- 
sible. 

The  importance  of  good  blast  machines,  and  of  the  application  of 
as  strong  a  pressure  as  the  fuel  will  bear,  will  be  still  more  appa- 
rent, if  we  reflect  that  the  degree  of  heat  depends,  to  a  great  extent, 
on  the  draught.  As  the  highest  heat  is,  in  almost  every  case,  most 
favorable  to  the  amount  of  fuel  consumed,  it  is  evident  that,  if  no 
other  advantage  accompanies  the  strongest  pressure,  that  of  econo- 
mizing fuel  will  result  from  it.  But,  in  the  blast  furnace,  a  still 
weightier  consideration,  that  is,  the  quality  and  quantity  of  iron, 
demands  our  attention.  As  a  general  rule,  we  may  say  that  a  com- 
paratively small  quantity  of  dense  blast  will  be  productive  of  as 
high  a  heat  as  a  much  larger  quantity  of  weak  blast.  Therefore, 
pressure  is  an  equivalent  for  hot  blast. 


428  MANUFACTURE   OF   IRON. 


CHAPTER    VII. 

HOT  BLAST. 

THE  application  of  hot  blast  in  the  manufacture  of  iron  is  of  re- 
cent date.  Scarcely  twenty  years  have  elapsed  since  the  first  expe- 
riments relative  to  it  were  made.  To  write  a  history  of  this  im- 
provement is  not  our  purpose.  Though  it  has  attracted  considerable 
attention,  the  principles  which  it  involves  have  been  developed  in 
a  much  less  degree,  and  have  even  been  much  less  understood,  than 
one  might  have  expected.  We  shall  endeavor  to  illustrate  the  sub- 
ject with  clearness  and  simplicity. 

I.  Hot  Air  Apparatus. 

The  apparatus  for  heating  air  before  it  is  brought  in  contact  with 
the  fuel,  is  very  simple,  and  the  principle  it  involves  easily  under- 
stood. The  object  we  seek  to  secure  in  the  construction  of  an  air- 
heating  oven  is  that  the  air  shall  be  heated  only  to  a  certain  de- 
gree ;  for  we  shall  find  that,  from  any  degree  of  heat  beyond  this, 
no  advantage  is  to  be  derived.  Further,  an  apparatus  must  be  of 
such  a  form  as  to  heat  the  pipes  uniformly  ;  for,  if  the  fire  plays  too 
much  on  one  place,  the  metal  pipes  are  soon  injured.  This  appa- 
ratus, on  account  of  its  simplicity,  admits  of  a  variety  of  forms ;  but, 
in  general,  it  is  settled  that  the  horizontal  pipe  is  the  most  effectual 
with  respect  to  economy  of  fuel,  though  it  needs  modification  on 
account  of  the  material  from  which  it  is  made.  The  horizontal 
form  of  the  pipe  is  the  best,  for  the  same  reason  that  the  round  and 
horizontal  is  the  best  form  of  the  steam  boiler ;  that  is  to  say,  by 
means  of  this  form  the  greatest  effect  of  the  heat  applied  is 
secured.  Air-heating  pipes  should  be  made  of  gray  cast  iron, 
because  of  the  fusibility  of  other  metals,  and  of  the  facility  with 
which  wrought  iron  oxidizes,  being  in  contact  with  oxygen  on  both 
sides.  Nevertheless,  cast  iron  pipes  are  very  heavy,  and  they  will 
bend,  and  finally  break,  by  their  own  weight,  if  laid  horizontally, 
and  heated  in  that  position.  Pipes  of  a  vertical  form  will  resist  the 


HOT  BLAST. 


429 


influence  of  the  heat  better  than  those  of  any  other  form,  but  they 
are  less  favorable  conductors  of  heat.  Those  who  have  attempted 
to  make  improvements  on  the  air-heating  stove  have  sought  to 
unite  the  advantages  of  the  one  with  those  of  the  other.  Most  of 
the  forms  now  in  use  are  based  upon  this  principle. 

a.  Air-heating  stoves  are,  at  the  present  time,  reduced  to  two 
principal  forms  ;  the  circular  pipe,  and  the  vertical,  or  more  or  less 
inclined  pipe.     The  latter  appears  to  be  preferred.     Fig.  143  re- 
Fig.  143. 


Hot-blast  apparatus. 

presents  a  vertical  section  of  an  air-heating  stove,  with  round  pipes, 
which  scarcely  requires  explanation.  The  diameter  of  the  round 
pipes  is  generally  three  inches  inside,  and  that  of  the  two  straight 
and  lower  pipes,  fifteen  inches  or  less,  according  to  the  quantity 
of  air  which  is  to  be  passed  through  it.  The  cold  air  passes  in  at 
one  end  of  one  of  the  lower  straight  pipes,  and  out  at  the  opposite 
end  of  the  other  pipe,  which  is  more  clearly  shown  by  Fig.  144. 
The  apparatus  is  here  assumed  to  be  on  the  top  of  the  blast-furnace; 


430  MANUFACTURE    OF   IRON. 

no  fire-place  is  seen.     Fig.  143  shows  a  grate  ;  hence, 


*J-  '  .^paratus  is  designed  to  be  heated  by  separate  fuel.  That  shown 
,..y  ""ig.  144  is  heated  by  the  waste  heat  of  the  furnace.    The  num- 

Fig.  144. 


Air-heating  apparatus — longitudinal  section. 

ber  of  round  pipes  is  increased  or  diminished  according  to  the 
amount  of  air  to  be  heated.  The  distance  between  the  two  straight 
pipes  is  generally  four  feet,  which  will  make  the  diameter  of  the 
round  pipes  about  five  feet.  The  vertical  pipes  are  placed  as  near  as 
possible  to  each  other ;  sufficient  room  is  left  for  the  passage  of  the 
flame  from  the  furnace,  which  does  not  require  more  than  one  and 
a  half  or  two  inches.  In  the  mason  work  are  several  small  doors, 
by  means  of  which  the  pipes  may  be  cleaned,  for  on  the  surface  of 
the  latter  a  large  quantity  of  dust  and  carbonized  ashes  is,  in  the 
course  of  the  operation,  condensed.  Unless  the  pipes  are  frequently 
cleaned,  they  are  liable  to  burn.  More  or  less  draught  may  be 
given,  and  more  or  less  heat  generated,  by  the  damper  on  the 
chimney.  The  round  pipes  are  set  on  each  side  in  sockets,  and 
well  secured  by  careful  cementing.  If  we  wish  to  make  the  best 
use  of  the  heat,  the  grate,  or  the  entrance  of  the  flame,  should  be 
put  on  that  end  of  the  apparatus  from  which  the  hot  blast  is  let  off. 


HOT  BLAST. 


431 


b.  In  Fig.  145,  the  other  arrangement  of  the  heating  pipe  is 
represented.     It  differs  in  no  respect  from  the  one  just  exhibited, 

Fig.  145. 


Hot  blast,  heated  on  the  top  of  the  blast  furnace. 

except  in  the  fact  that  the  heating  pipes  are  straight  and  set  almost 
vertically,  connected  at  the  top  by  a  short  curved  pipe.  The  straight 
pipes  are  frequently  from  six  to  eight  feet  in  length  at  large  fur- 
naces; diameter  inside  five  inches;  metal  one  inch  thick. 

Other  forms  of  heating  apparatus  are  but  little  in  use,  and  are 
less  useful  than  those  described.  For  small  charcoal  furnaces,  an 
apparatus  five  feet  long,  consisting  of  eight  pipes,  is  sufficient. 
At  large  anthracite  coke  furnaces,  we  meet  with  an  apparatus 
of  thirty  and  more  pipes  for  each  furnace.  No  general  rule  with 
respect  to  the  number  of  pipes,  and  the  extent  of  surface  required, 
can  be  given;  but  conclusions  derived  from  experience  prove 
that  a  surface  from  three  to  four  feet  square  is,  when  exposed  to 
the  heating  flame,  large  enough  to  heat  an  amount  of  air  sufficient 


432 


MANUFACTURE   OF   IRON. 


for  one  ton  of  iron  per  week.  The  heat,  in  the  interior  of  such  a 
stove,  is  not  very  great ;  but  the  furnace,  and  frequently  the  whole 
apparatus,  are  lined  with  fire  brick.  This  is  more  durable,  and 
saves  more  fuel  than  red  or  common  brick.  Heavy  brick-work  is 
very  advantageous  at  hot  air  furnaces,  for  changes  in  the  tempera- 
ture of  the  blast  should  be  avoided. 

c.  At  a  blast  furnace,  where  hot  blast  is  employed,  the  tuyere 
cannot  be  left  open  around  the  nozzle.  We  are  thus  deprived  of 
the  means  of  getting  at  it  directly.  As  it  is  necessary  that  the 
tr  ire  should  be  cleaned,  an  arrangement  is  made  to  get  at  it  from 
f  cap  of  the  pipe  near  a,  Fig.  146.  A  small  hole  in  the  cap 

Fig.  146. 


Hot-blast  stove,  air-pipes,  and  tuyere  poker. 

admits  a  three-quarter  inch  round  rod,  which  is  pushed  in  until  it 
reaches  the  tuyere.  This  hole  is  closed  by  a  short  iron  stopper. 
The  cap  0,  on  which  the  nozzle  is  fastened,  must  be  light  and  easily 
movable,  above  the  valve ;  for,  as  we  have  stated,  some  work  is 
necessary  to  be  done  at  the  tuyere.  The  cap  and  nozzle  should  be 
light,  and  movable  with  facility,  and  therefore  the  best  material 
from  which  they  can  be  made  is  sheet  iron.  In  case  the  heating- 
stove  is  at  the  top  of  the  blast  furnace,  the  blast  pipe  may  be  led 
from  above  to  the  tuyere.  This  is  advantageous  where  but  one 
tuyere  is  to  be  supplied ;  but  where  two  or  more  tuyeres  are  in 


HOT  BLAST.  433 

the  furnace,  it  will  be  found  preferable  to  lay  the  pipes  below  the 
bottom  stone.  In  case  there  is  no  surplus  of  heat,  and  we  wish  to 
preserve,  as  much  as  possible,  the  heat  in  the  blast,  the  hot  air- 
pipe,  leading  from  the  stove  to  the  tuyeres,  may  be  packed  in  sand, 
and  laid  in  a  wooden  box;  or,  it  may  be  surrounded  by  a  coating 
of  loam.  The  pipes  closest  to  the  fire  must  be  secured  against  the 
violent  action  of  the  flame,  by  a  protection  of  brickwork  or  fire- 
clay. It  is  advisable  to  have  a  direct  communication  between  the 
tuyere  and  the  blast  machine;  cold  blast  can  thus  be  led  directly, 
or  around  the  heating  stove,  into  the  furnace  when  it  is  required. 
The  hot  air-pipes  are  sometimes  injured  without  apparent  cause, 
and  the  stopping  up  of  the  furnace  would  result  from  this  accident, 
were  we  to  stop  the  blast  machine. 

d.  In  the  cap  of  each  nozzle  there  is  a  hole,  to  which  the  manome- 
ter is  attached;  this  enables  us,  by  introducing  a  thermometer  for  a 
short  time,  to  measure  the  degree  of  heat  of  the  blast.  The  ther- 
mometer must  be  sufficiently  long  to  indicate  the  degrees  of  heat 
below  the  boiling  point  of  mercury ;  a  greater  length  would  be 
superfluous.  Glass  instruments  are  very  liable  to  be  broken,  par- 
ticularly at  furnaces ;  and  as  it  is  a  matter  of  considerable  import- 
ance to  know  the  temperature  of  the  blast,  a  more  practical  means 
of  measuring  heat,  namely,  by  alloys  of  metal,  is  resorted  to.  A 
small  quantity  of  such  a  composition,  or  of  pure  lead,  is  put  into 
a  small  vessel  of  copper  or  iron,  which  is  fastened  to  a  thin  wire, 
and  let  down  into  the  centre  of  the  blast  pipe.  After  obtaining  a 
composition  which  melts  at  a  certain  temperature,  no  further  ex- 
periments are  necessary;  and  such  a  test  may  be  applied  when 
a  doubt  arises  in  our  minds  as  to  the  heat  of  the  blast.  For  prac- 
tical purposes,  it  is  unnecessary  to  know  exactly  the  degree  of  this 
heat.  An  approximation  to  correctness  will,  in  this  case,  answer 
every  purpose.  Pure  lead  melts  at  470°;  mercury  boils  at  660°; 
tin  melts  at  380°,  tinner's  solder  at  410°,  type  metal  at  350°, 
and  a  mixture  of  type  metal  and  tinner's  solder  at  300°.  We 
shall  annex  a  few  alloys,  which  may  be  used  to  measure  lower 
temperatures;  but  with  the  caution  that  the  melting  point  of  the 
alloys  is  somewhat  raised  after  each  experiment.  A  mixture  of 
five  parts  of  lead,  three  parts  of  tin,  and  eight  parts  of  bismuth, 
melts  at  the  heat  of  boiling  water,  or  212°.  The  addition  of  mer- 
cury makes  it  still  more  fusible.  Three  parts  of  bismuth,  one  of 
lead,  and  one  of  tin,  melt  at  200°.  Bismuth  melts  at  480° ;  but  its 
28 


434  MANUFACTURE   OF   IRON. 

alloys  are  very  fusible.  With  the  addition  of  bismuth  to  tinner's 
solder,  all  the  degrees  between  200°  and  500°  may  be  produced. 
Nevertheless,  a  mercury  thermometer,  inclosed  in  a  metal  capsule, 
and  suspended  on  wire,  to  prevent  the  contact  of  the  glass  and 
metal,  is  the  best  and  easiest  method  of  measuring  the  heat  of  the 
blast. 

II.   Theory  of  Hot  Blast. 

Hot  air,  for  the  alimentation  of  combustion,  has  been  employed 
for  a  number  of  years ;  still,  a  clear  and  comprehensive  demon- 
stration of  the  cause  and  effects  of  its  action,  in  the  manufacture 
of  iron,  remains  yet  a  desideratum.  We  shall  endeavor  to  elucidate 
the  subject  as  clearly  as  possible.  The  effect  of  the  application 
of  hot  blast  is  threefold:  First,  it  saves  fuel  in  the  direct  pro- 
portion of  the  temperature  of  the  aliment  to  the  temperature  of 
combustion.  Secondly,  the  supply  of  hot  air  to  smelting  ope- 
rations increases  the  reducing  power  of  the  gases,  by  promoting 
the  combination  of  oxygen  and  carbon.  Thirdly,  it  promotes 
the  chemical  union  of  the  particles  of  fluxes.  This  union  is  occa- 
sioned by  heat,  and  may  therefore  be  considered  a  mechanical 
operation. 

a.  The  first  of  these  advantages  is  limited  in  its  extent;  for,  if  we 
heat  the  air,  designed  for  the  nourishment  of  fuel,  beyond  a  certain 
degree,  it  ceases  to  add  to  the  increase  of  temperature,  as  well  as 
to  economize  fuel.  A  theoretical  explanation  of  this  fact  may  be 
found  in  the  greater  facility  with  which  matter  combines  when 
warm  with  excited  polarity.  This  polarity  occasions  a  saving  of 
fuel,  because,  where  other  conditions  exist,  particles  of  cold  air  may 
escape  uncombined,  and,  of  course,  absorb  heat  and  reduce  tem- 
perature. Hot  blast  in  some  measure  prevents  this  result.  But  if 
all  the  oxygen  is  combined  with  the  carbon,  no  further  rise  of  tem- 
perature is  possible.  In  fact,  were  all  the  oxygen  of  cold  air  to 
combine  with  carbon  and  hydrogen,  and  were  no  air  to  escape 
but  that  which  formed  water  or  carbonic  acid,  there  would  be  no 
rational  basis  upon  which  a  rise  of  temperature,  or  economy  of 
fuel  by  hot  blast,  could  be  hypothecated.  Several  authors  have 
attempted,  by  very  elaborate  theoretical  investigations,  to  demon- 
strate that  hat  air  produces  a  higher  temperature,  independently  of 
the  above  cause ;  and  they  have  endeavored  to  show  that  the  tem- 
perature of  combustion  may  be  raised,  by  a  judicious  application 
of  hot  blast,  500°  beyond  the  point  at  which  combustion  takes 


HOT  BLAST.  435 

place  with  cold  air.  But  we  must  be  permitted  to  doubt  the  cor- 
rectness of  a  conclusion,  arrived  at  by  means  of  mathematical  cal- 
culus, in  relation  to  a  subject  concerning  which  the  laws  of  chemis- 
try alone  are  competent  guides.  These  are  simple  and  compre- 
hensive, and  based  upon  actual  experiments ;  and  they  do  not  favor 
such  abstract  views  concerning  the  increase  of  temperature  by 
means  of  hot  air,  but  they  clearly  explain  an  increase  caused  by  a 
given  combustion.  If  the  increase  of  temperature  depends  upon 
the  facilities  which  hot  air  imparts  to  combustion,  it  is  evident  that 
there  must  be  a  point  in  the  temperature  of  the  hot  air  at  which 
its  economical  advantages  cease — that  there  must  be  a  point,  in  fact, 
at  which  the  largest  quantity  of  oxygen  is  converted  into  carbonic 
acid.  If  the  alimentary  air  is  cold,  a  diminution  of  temperature, 
in  consequence  of  imperfect  combustion,  will  take  place  ;  if  it  is  too 
hot,  a  lower  temperature  will  result,  because  the  combustion  is  so 
thorough,  that  carbonic  oxide  gas,  instead  of  carbonic  acid  gas,  will 
be  formed.  By  referring  to  the  second  chapter,  this  matter  may  be 
more  clearly  understood.  The  highest  heat  obtained  from  the  com- 
bustion of  fuel  and  the  application  of  hot  air,  which  results  in  ad- 
vantage, has  been  found  to  be  about  500°,  or,  the  melting  point 
of  lead.  This  number,  of  course,  varies  according  to  the  kind  of 
fuel  employed.  A  higher  heat  will  be  advantageous  if  we  burn 
anthracite,  and  a  far  lower  temperature,  if  we  burn  charcoal.  If 
we  do  not  need  a  high  temperature  for  a  given  operation,  we  may 
economize  fuel  by  spreading  the  heat  over  a  large  surface. 

Hot  air  effects  a  saving  of  fuel  in  proportion  as  its  temperature  is 
the  complement  of  that  in  the  furnace.  In  nearly  every  instance  of 
combustion,  unburnt  air  passes  through  the  fuel.  The  lower  the 
temperature  of  combustion,  the  greater  the  quantity  of  air  which 
will  pass  uncombined ;  that  is  to  say,  the  heat  of  the  blast  or  the 
nourishing  air,  which  adds  directly  to  the  heat  of  combustion,  will 
be  the  more  apparent,  the  lower  the  heat  in  the  furnace. 

From  these  considerations,  we  may  conclude  that,  where  the  high- 
est possible  temperature  is  desirable,  the  application  of  hot  air  in 
combustion  is  indispensable.  But  there  is  a  limit  to  this  applica- 
tion ;  and  the  air  suitable  for  one  kind  of  fuel  may  be  too  hot  or 
too  cold  for  another  kind.  There  is  no  direct  saving  of  fuel  in  cases 
in  which  the  air  is  to  be  heated  by  separate  fuel,  but  only  in  cases 
where  it  can  be  heated  by  the  waste  heat  of  the  furnace  itself,  or 
by  some  other  means.  The  per  centage  of  fuel  saved,  in  the  latter 
case,  is  equal  to  the  temperature  applied  to  it.  It  thus  follows  that, 


436  MANUFACTURE   OF  IRON. 

in  a  furnace  heated  to  4000°,  to  which  air  of  400°  is  applied,  ten 
per  cent,  of  fuel  will  be  saved ;  but  if  the  temperature  in  the  fur- 
nace is  only  2000°,  and  that  of  the  alimentary  air  400°,  a  saving 
of  20  per  cent,  will  be  realized.  This,  however,  applies  only  to  a 
combustion  which  is  imperfect,  and  occasioned  by  a  too  liberal  sup- 
ply of  air.  Where  the  combustion  is  smothered,  the  application 
of  hot  blast  is  disadvantageous  ;  as  far,  at  least,  as  economy  of  fuel 
is  concerned,  no  benefit  results  from  it. 

The  above  may  be  said  to  be  the  general  advantages  derivable 
from  hot  blast;  but  these  are  not  so  striking  as  those  obtained  in 
some  specific  cases.  Hot  air  promotes  the  combination  of  the  oxy- 
gen and  fuel.  In  metallurgy,  this  is  a  matter  of  great  importance, 
for  we  are  constantly  dealing  with  oxides  which  must  be  reduced 
to  metal.  Carbonic  acid  will  not  reduce  any  oxide ;  hence,  com- 
bustion is  to  be  carried  so  far  as  to  form  carbonic  oxide.  Warm 
air  is,  of  course,  far  better  adapted  to  effect  this  result  than  cold 
air.  For  these  reasons,  its  behavior  in  the  blast  furnace  demands 
the  especial  attention  of  the  manufacturer. 

b.  In  the  blast  furnace,  the  fundamental  object  which  we  seek 
to  secure  is  the  combination  of  every  atom  of  oxygen  with  carbon. 
By  applying  very  hot  blast,  so  as  to  form,  as  soon  as  possible,  car- 
bonic oxide  in  the  hearth,  the  reviving  process  would  be  improved  ; 
but,  in  such  a  case,  the  temperature  would  be  so  low  that  good 
cast  iron  could  not  melt  at  all.  A  temperature  of  the  blast  best 
calculated  to  produce  the  highest  heat  in  combustion  may,  there- 
fore, be  considered  the  most  advantageous.  If  we  carry  the  re- 
duction of  those  iron  ores  which  are  always  more  or  less  impure, 
too  far,  a  great  deal  of  foreign  matter  is  reduced ;  the  pig  iron  will 
be  very  much  contaminated  with  it.  This  disadvantage  is  greatly 
augmented  by  the  high  temperature  in  the  hearth ;  this  causes  a 
high  state  of  electrical  excitement  in  the  iron  and  its  impurities, 
which  thus  combine  very  intimately.  A  stronger  chemical  affinity 
than  that  by  which  the  combination  was  produced,  is  required  to 
dissolve  this  union.  If  we  wish  to  work  to  the  greatest  advantage 
with  respect  to  economizing  fuel  in  a  blast  furnace,  we  should  be 
careful  that  the  temperature  is  highest  at  the  tuyeres.  Where  qua- 
lity alone  is  sought  for,  the  heat  should  be  highest  above  the  tuy- 
eres; in  this  case,  the  iron  will  be  cooled,  and  its  impurities  oxi- 
dized, before  it  settles  down  into  the  crucible.  A  gradual  increase 
of  heat  from  the  top  of  a  blast  furnace  down  to  the  tuyeres  is  the 
object  at  which  we  should  aim ;  and  this  can  be  realized  by  pro- 


,  HOT  BLAST.  437 

ducing,  with  a  certain  degree  of  heat  in  the  blast,  the  highest 
heat  exactly  at  the  tuyere. 

c.  Another  equally  important  advantage  of  hot  blast  is  its  me- 
chanical influence  upon  cinder.  The  particles  of  matter  which 
enter  into  the  composition  of  cinder  will  be  exposed  by  a  high 
heat,  and  their  affinity  for  each  other  increased  ;  the  consequence 
is,  a  greater  fusibility  of  the  cinder  and  a  saving  of  limestone. 
Cinder  soon  cools,  particularly  if  it  is  of  a  silicious  nature;  the 
blast  of  a  furnace,  always  working  more  or  less  upon  it,  chills 
it ;  in  this  state,  the  particles  of  melted  iron  will  not  pass  through 
it ;  hence,  it  will  flow  slowly  over  the  dam.  Hot  air  keeps  it  in  its 
highest  state  of  fluidity;  by  that  means  the  descent  of  the  iron  and 
the  removal  of  the  cinder  are  promoted.  But  that  which  is  bene- 
ficial to  the  cinder  is  very  injurious  to  the  iron;  that  which 
makes  the  cinder  more  liquid,  and  imparts  to  it  a  more  homoge- 
neous texture,  causes  the  impurities  to  unite  more  strongly  with  the 
iron.  This  is  another  instance  in  which  we  cannot  increase  the 
temperature  of  hot  blast  beyond  given  limits.  Unless  the  blast  has 
been  too  hot,  the  combination  of  impurities  and  iron  can  be,  in  a 
great  measure,  dissolved  in  the  puddling  furnace ;  but  not  so  well 
in  the  forge  fire. 

The  advantages  arising  from  hot  blast  and  cinder  have  brought 
into  use  certain  refractory  ores  and  fuel  which,  before  their  applica- 
tion, were  regarded  as  comparatively  worthless.  There  is  no  ma- 
terial, however  small  the  amount  of  iron  it  may  contain,  or  in  what- 
ever form  or  combination  it  may  exist,  which  cannot  be  revived  by 
a  judicious  application  of  hot  blast.  If  the  forges  could  work  any 
quality  of  pig  iron  to  advantage,  the  blast  furnace  might  be  profit- 
ably employed  upon  cheap  productions.  By  applying  hot  blast, 
we  are  enabled  to  revive  iron  from  the  poorest  kind  of  silicious  and 
aluminous  ores,  to  reduce  the  protoxide  in  the  silicates,  and  to 
revive  iron  from  forge  cinders.  If  the  quality  of  the  product  would 
satisfy  the  forge-man,  the  application  of  hot  blast  would  probably 
reduce  the  price  of  pig  iron  in  the  anthracite  and  bituminous  coal 
regions  to  a  considerable  extent. 

d.  It  will  doubtless  be  as  appropriate  in  this  as  in  any  other  place 
to  make  a  few  remarks  relative  to  the  causes  of  bad  iron,  result- 
ing either  from  hot  blast  and  imperfectly  prepared  ores,  or  from 
forge  cinder  and  the  native  silicates.  It  is  a  law  of  chemistry  that 
matter  can  be  dissolved,  under  favorable  circumstances,  in  a  solv- 
ent which,  under  ordinary  conditions,  would  not  affect  it.  Silex, 


438  MANUFACTURE   OF  IRON.  * 

if  in  chemical  union  with  any  substance,  such  as  oxide  of  iron, 
can  be  dissolved  by  hydrochloric  acid  under  any  condition ;  -while 
silex  in  an  uncombined  state  is  not  acted  upon  by  it.  Silex,  dis- 
solved in  potash  or  soda,  and  precipitated  from  that  solution  by 
an  acid,  is  soluble  in  water ;  but  if  the  precipitated  silex  is  dried 
and  heated,  it  is  insoluble  in  any  menstruum  whatever.  This  be- 
havior of  the  silex  is,  in  a  greater  or  less  degree,  the  same  as  that 
of  most  other  substances.  To  investigate  the  cause  of  this  differ- 
ence of  solubility  in  matter  of  the  same  constitution,  does  not  be- 
long to  our  department.  It  is  sufficient  to  know  the  fact.  We 
shall  make  use  of  it,  to  explain  the  cause  of  the  behavior  of  iron 
ores,  with  respect  to  the  quality  of  the  iron  revived.  The  object  of 
preparing  or  roasting  iron  ore  is  simply  this:  to  expel  from  it  fugi- 
tive foreign  matter.  Roasting  opens  the  ore,  and  effects  a  more  tho- 
rough separation  of  the  oxide  of  iron  from  the  foreign  matter.  It  is 
the  latter  object  alone  which  concerns  us  at  present.  No  foreign 
matter  interferes  so  much  with  our  operations  as  silex ;  few  other 
substances  interrupt  our  business.  Silex,  as  a  strong  acid,  and 
in  consequence,  probably,  of  some  unknown  specific  quality,  has 
a  remarkably  strong  affinity  for  the  protoxide  of  iron.  It  is  a 
composition  of  an  unknown,  at  least  not  well  known,  element, 
silicon  and  oxygen.  This  element  has  a  very  strong  affinity  for 
oxygen;  one  atom  of  silicon  combines  with  three  atoms  of  oxygen, 
or  very  nearly  fifty  parts  by  weight  of  the  one  with  fifty  parts  of 
the  other.  From  iron  ores — in  which  an  intimate  connection  ex- 
ists between  the  silex  and  the  oxide  of  iron — the  iron  cannot  well 
be  revived,  unless  a  portion  of  silicon  is  also  revived.  This  will 
appear  the  more  reasonable,  when  we  reflect  that  silicon  has  as 
strong  an  affinity  for  the  metallic  iron  as  silex  has  for  the  oxides  of 
iron.  In  manufacturing  steel,  every  effort  is  made  to  purify  the  iron; 
and  yet  the  best  steel  always  contains  silicon.  The  more  intimate  the 
connection  between  the  oxide  and  the  silex  in  the  ore,  the  greater 
will  be  the  amount  of  silicon  which  the  revived  iron  will  contain. 
The  present  case  is  similar  to  those  in  which  a  silicate,  or  any  iron 
ore,  is  dissolved  in  hydrochloric  acid.  Here,  the  silex  parts  more 
readily  with  oxygen  than  with  iron.  There  would  be  very  little  pros- 
pect of  separating  iron  from  silicon,  had  not  iron  a  great  affinity  for 
carbon.  Open,  well-roasted  ores  absorb  more  carbon  than  close 
ores ;  but  forge  cinders  or  silicates  absorb  none  at  all.  The  first  make 
gray  iron,  which,  notwithstanding  the  large  amount  of  silicon  they 
often  contain,  can  be  worked  to  advantage.  The  latter  always  pro- 


HOT  BLAST.  439 

duce  hard,  cold-short  iron,  and  they  generally  contain  less  silex  than 
the  first  ores.  Carbon,  if  in  mechanical  admixture,  as  in  gray  pig 
iron,  keeps  the  iron  porous ;  oxygen  will  have  access  to  the  interior; 
and  as  silicon  has,  at  a  low  temperature,  a  greater  affinity  for  oxy- 
gen than  it  has  for  iron  or  carbon,  it  will  oxidize  before  either  of  the 
latter.  Upon  this  hypothesis,  we  can  explain  the  improvement  of 
pig  iron  by  means  of  cold  water.  Steam  may  find  access  to  the 
interior  of  the  iron,  if  the  latter  is  suddenly  chilled  and  crystalized. 
We  shall  refer  more  extensively  to  this  subject  in  the  article  on 
steel.  Silex  has  little  affinity  for  carbon,  so  has  silicon;  but  the 
latter  has  so  great  an  affinity  for  oxygen,  that  it  can  be  oxidized 
only  to  a  certain  extent,  if  in  a  body :  the  resulting  silex  covers 
the  silicon,  and  prevents  its  further  oxidation.  The  heat  produced 
by  oxidation,  and  the  cohesion  of  the  silex,  are  very  great.  Carbon 
does  not  combine  with  oxygen  at  a  low  temperature.  If,  there- 
fore, silicon  is  contained  in  cold  gray,  or  white  iron,  and  if,  in  this 
divided  state,  it  is  oxidized,  it  will  not  cause  the  temperature  to  be 
raised  sufficiently  high  to  burn  the  carbon,  and  the  pig  iron  or 
metal  may  retain  all  its  carbon,  though  the  silicon  will  be  oxidized 
to  silex  ;  the  latter  is  of  no  injury  whatever  to  iron.  But,  if  iron, 
containing  silicon  and  carbon,  is  heated  so  far  that  its  carbon  will 
unite  with  oxygen,  and  is  then  exposed  to  a  liberal  access  of  air — 
whether  in  the  blast  furnace,  the  finery,  charcoal  forge,  or  pud- 
dling furnace — it  will  lose  its  carbon,  it  will  be  white.  Here  the 
high  temperature  is  the  cause  of  the  combustion  of  carbon.  The 
burning  of  the  silex  will,  as  a  matter  of  course,  be  the  cause  of 
the  conversion  of  a  portion  of  iron  into  protoxide,  with  which  it  will 
combine;  this  protoxide  is,  in  turn,  reduced  to  metallic  iron  by 
the  carbon.  Such  a  process  will  always  take  place  in  large  or 
small  particles  of  melting  iron.  If  a  drop  of  such  iron  is  exposed 
to  oxygen,  the  latter  will  oxidize  its  surface,  and  the  result  will  be 
silex,  iron,  and  carbon.  But  in  this  heat,  carbon  has  a  greater 
affinity  for  oxygen  than  iron ;  and  the  oxide  of  iron,  which  may 
have  been  formed,  is  reduced  by  the  carbon  from  the  interior  of 
the  drop.  In  this  way,  the  pig  iron  is  deprived  of  its  carbon,  its 
cohesion  increased,  and  its  fusibility  diminished.  If  the  amount 
of  silicon  is  disproportionate  to  that  of  carbon,  the  iron  is  almost 
beyond  improvement,  for  that  heat  which  will  melt  it  will  oxi- 
dize it,  and  transform  nearly  all,  or  a  part,  of  it  into  a  rich  silicate, 
without  improving  the  iron  which  remains,  and  which  may  be 
yielded  from  such  impure  silicious  metal.  Hot  blast  is,  in  this 


440  MANUFACTURE   OF   IRON. 

case,  more  injurious  than  cold  blast,  for  it  increases  the  tempera- 
ture, and  hence,  the  affinity  of  carbon  for  oxygen;  but  it  diminishes 
the  affinity  of  iron  and  silicon  for  oxygen,  and  increases  the  affinity 
of  the  one  for  the  other. 

From  these  considerations,  we  may  ascertain  to  what  extent 
hot  blast  may  be  injurious.  In  endeavoring  to  obviate  such 
difficulties,  we  are  sometimes  led  into  expenses  which  our  busi- 
ness cannot  bear.  A  very  effective  remedy  against  impure  ores 
is  found  in  roasting  them ;  but  neither  the  most  attentive  roasting 
and  breaking  of  ore  and  coal,  nor  the  selection  of  certain  qualities, 
will  ever  lead  to  the  manufacture  of  cheap  pig  iron.  The  rolling- 
mills  would  gain,  but  the  furnaces  would  be  hampered.  The  best 
policy  which  the  iron  manufacturer  can  pursue,  in  view  of  the  pre- 
sent social  relations  which  exist  in  this  country,  is  to  endeavor  to 
diminish  labor  by  means  of  scientific  improvements.  These,  to  be 
sure,  as  in  the  present  case,  are  realized  only  with  difficulty;  but 
he  should  be  encouraged  by  reflecting  that  few  useful  inventions  are 
introduced  which  are  not  the  result  of  energy  and  perseverance. 
An  invention  is  generally  appreciated  in  the  ratio  of  the  difficulties 
which  it  overcomes.  At  present,  the  best  method  of  improving 
impure  pig  iron  is  suddenly  to  cool  it,  in  thin  plates.  Other 
methods  of  accomplishing  this  result  have  been  already  described. 

III.   General  Remarks  on  Hot  Blast. 

Heated  air  has  sometimes  been  applied  at  the  wrong  place.  We 
shall  allude  to  hot  blast  only  as  it  is  available  in  the  iron  busi- 
ness; for,  in  fact,  the  instances  are  few  in  which  it  is  of  advantage 
in  other  departments  of  labor.  In  its  application  to  the  manufac- 
ture of  iron,  its  advantages  are  great,  but  they  are  limited  to  the 
blast  furnace.  All  other  operations  involved  in  this  manufacture 
are,  to  a  greater  or  less  extent,  oxidizing  processes,  in  which  warm 
air  is  of  no  advantage  in  the  sense  in  which  it  is  beneficial  to  the 
blast  furnace  operations.  Hot  blast  may  be  considered  an  advan- 
tage, so  far  as  the  direct  amount  of  heat  in  the  air  is  proportional 
to  the  heat  generated;  provided  the  heat  of  the  alimentary  air  is 
derived  from  those  conditions  under  which  waste  heat  is  the  gene- 
rator of  the  heat  in  the  blast.  If  extra  fuel  is  employed  in  cases 
where  our  only  object  is  to  generate  heat,  without  reference  to 
other  advantages,  hot  air,  as  an  important  economizing  agent  in 
the  production  of  heat,  will  prove  only  an  illusion;  except  in  the 
reviving  process,  it  is  of  no  value,  and  even  in  this  process,  it  is 


HOT    BLAST.  441 

of  value  only  to  a  certain  extent.  Hot  blast  has  been  applied  to 
charcoal  forges,  and  is  still  so  applied ;  but  experience  clearly 
shows  that  it  injures  the  quality  of  the  iron  manufactured.  Hence, 
it  offers  no  possible  advantages,  for  what  is  gained  in  quantity  is 
lost  in  quality.  Charcoal  forges  are  valuable,  in  our  country,  as  a 
means  of  producing  quality.  If  that  object  is  compromised,  which 
is  surely  the  case  where  hot  blast  is  employed,  charcoal  iron  will 
be  brought  to  a  level  with  puddled  iron.  This  would  be  the  surest 
method  of  making  charcoal  forges  unprofitable.  In  the  Catalan 
forge,  hot  blast  may  be  employed  advantageously  in  the  melting 
down  of  the  ore  or  cinder ;  but  in  the  breaking  up  or  blooming, 
cold  blast  should  be  employed. 

Hot  air  is  of  but  little  advantage  in  puddling  and  re-heating  fur- 
naces, or  sheet  iron  ovens,  where  bituminous  fuel,  such  as  wood, 
turf,  or  bituminous  stone  coal,  is  used.  If  we  burn  anthracite  in 
these  furnaces,  we  may  realize  a  moderate  gain  by  hot  air,  provided 
the  air  can  be  heated  by  waste  heat.  This  remark  may  be  par- 
ticularly applied  to  the  re-heating  furnace,  where  large  piles  of  iron 
are  to  be  re-heated;  for  free  oxygen  is  generally  contained  in  the 
flame  of  this  furnace  even  in  the  highest  heat.  This  oxygen,  in 
some  measure,  works  destructively  on  the  iron  to  be  re-heated.  Its 
amount  will  be  greater  in  an  anthracite  re-heating  furnace  than 
in  any  other;  still,  it  may  be  reduced  by  the  employment  of  hot 
air. 

At  the  blast  furnace,  economy  of  fuel  is  an  important  object; 
not  so  much  because  fuel  is  valuable  in  itself,  but  because  wages 
are  high;  the  handling  of  fuel,  as  well  as  the  keeping  of  a  fire, 
requires  labor.  For  these  reasons,  air  is  generally  heated  at  the 
top  of  the  furnace.  Coke  furnaces  may  be  considered,  with  the 
exception  of  a  few  anthracite  furnaces,  the  only  ones  at  which  the 
blast  is  heated  by  separate  fuel,  and  where  extra  labor  is  required. 
The  top  flame  of  any  blast  furnace  contains  far  more  heat  than 
any  air  apparatus  requires.  Apparatus  which  is  not  constructed 
on  the  principle  of  economizing  fuel,  is  the  most  practical.  The 
air  stove  should  be  so  constructed  as  to  secure  durability  and  sim- 
plicity. The  flame  may  be  conducted  directly  from  the  top  to  the 
stove;  or  the  gas  may  be  tapped  below  the  top,  and  conducted  in 
pipes  or  channels  to  the  stove,  just  as  we  choose;  either  method 
is  good,  and  by  either  method  we  may  obtain  as  much  heat  as  we 
require.  Where  the  steam  which  drives  the  blast  machine  is  gene- 
rated at  the  top  of  the  furnace,  as  is  generally  the  case,  it  is  advis- 


442  MANUFACTURE   OF  IRON. 

able  to  place  the  air-heating  stove  at  the  end  of  the  steam  boilers  ; 
for  there  is  sufficient  heat  left,  after  the  flame  has  passed  under  the 
steam  boilers,  to  heat  the  blast  to  any  degree  which  may  be  con- 
sidered profitable.  What  makes  this  arrangement,  common  at  the 
anthracite  furnaces,  more  profitable,  is  the  fact  that  the  gas,  by  the 
time  it  passes  the  steam  boilers,  is,  in  some  measure,  cooled,  and 
not  sufficiently  hot  to  injure  the  air-pipes.  This  result  frequently 
occurs  where  the  apparatus  is  put  directly  to  the  trunnel-head. 

The  economical  advantages  arising  from  the  application  of  hot 
blast,  casting  aside  those  cases  in  which  cold  blast  will  not  work  at 
all,  are  immense.  The  amount  of  fuel  saved,  in  anthracite  and  coke 
furnaces,  varies  from  thirty  to  sixty  per  cent.  In  addition  to  this, 
hot  blast  enables  us  to  obtain  nearly  twice  the  quantity  of  iron 
within  a  given  time  that  we  should  realize  by  cold  blast.  These 
advantages  are  far  more  striking  with  respect  to  anthracite  coal 
than  in  relation  to  coke,  or  bituminous  coal.  By  using  hard  char- 
coal, we  can  save  twenty  per  cent,  of  fuel,  and  augment  the  product 
fifty  per  cent.  From  soft  charcoal  we  shall  derive  but  little  benefit, 
at  least  where  it  is  necessary  to  take  the  quality  of  iron  into  con- 
sideration. 


WASTE  HEAT  AND  GAS.  443 


CHAPTER   VIII. 

WASTE  HEAT  AND  GAS. 

WASTE  heat  is  an  article  so  abundant  in  iron  manufactories  that 
a  profitable  method  of  using  it  should  be  deemed  an  object  of  con- 
siderable importance.  Its  application,  owing  to  various  causes,  has 
sometimes  been  attended  with  only  partial  success.  This  partial 
success  is  to  be  attributed,  in  many  instances,  to  the  fact  that  it 
has  been  applied  at  the  wrong  place,  in  which  case,  the  nature  of 
the  heat  required  is  not  understood.  If  we  consider  the  very  limited 
capacity  of  iron  for  heat,  and  the  high  temperature  at  which  the 
gases  escape,  the  amount  of  heat  wasted  in  iron  works  will  prove 
to  be  immense.  In  a  re-heating  furnace,  for  example,  a  small 
amount  of  the  caloric  generated  would  suffice  to  heat  the  iron  to 
a  welding  heat ;  but  a  great  deal  of  this  heat  is  lost,  because  some 
time  must  elapse  before  the  heat  of  the  furnace  can  be  imparted  to 
the  iron ;  besides,  with  the  welding  heat  the  flame  escapes.  The 
most  successful  method  of  saving  fuel  in  iron  manufactories  is  to 
save  time ;  if  we  gain  one-fourth  of  a  given  period  of  time,  we  save, 
in  most  cases,  twenty-five  per  cent,  of  fuel.  If  we  make  six  heats  in 
a  puddling  furnace,  instead  of  four,  we  save  thirty-three  per  cent. 
If  a  re-heating  furnace  of  a  given  size  can  be  made  to  produce  eight 
tons  of  iron  a  day  instead  of  four,  nearly  fifty  per  cent,  of  fuel  will 
be  saved.  This  is  the  true  principle  on  which  economy  of  fuel  in 
iron  manufacture  is  based.  But,  even  when  economy  is  carried  to 
the  farthest  extent,  we  may  imagine  that  the  waste  heat  which  is 
lost  amounts  to  at  least  eighty  or  ninety  per  cent,  of  that  gene- 
rated. In  employing  waste  heat,  we  are  too  apt  to  confound  the 
quality  with  the  quantity  of  heat.  We  see  an  immense  amount 
of  heat  wasted  ;  but  we  do  not  reflect  that  the  temperature  of  this 
heat  is  very  low,  and  that  it  is  a  want  of  intensity  which  makes 
its  application  very  limited.  We  possess  no  means  to  raise  this 
temperature  ;  at  least,  there  are  few  instances  in  which  it  can  be 


444  MANUFACTURE    OF  IRON. 

raised  to  such  a  degree  as  to  make  it  useful  in  our  manufacturing 
apparatus.  Waste  heat  cannot  be  generally  employed,  on  ac- 
count of  the  chemical  composition  of  the  flame,  or  gases,  which 
contain  the  heat.  The  waste  flame  of  the  furnace  contains  a  greater 
or  less  amount  of  free  oxygen,  or,  at  least,  a  large  amount  of 
watery  vapors,  which  is  the  same  thing,  for  these  vapors  are  d 
composed  when  in  contact  with  hot  iron.  An  excess  of  free 
gen,  and  low  temperature,  are,  in  most  cases,  highly  disadvan- 
tageous. For  example,  the  waste  heat  of  a  re-heating  furnace  would 
be  of  no  more  service  than  the  flame  from  green  wood.  We  can- 
not use  it  in  a  puddling  furnace,  in  which  inferior  pig  iron  is  con- 
verted. In  most  cases,  its  employment  would  interfere  with  im- 
portant operations,  in  which  case  a  loss  would  be  experienced  which 
the  gain  in  fuel  could  not  repay. 

I.    Waste  Heat. 

a.  The  waste  heat  of  mill  furnaces  may  be  advantageously  em- 
ployed to  generate  steam,  and  to  propel  rollers,  hammers,  squeez- 
ers, and  blast  .machines.  This  is  the  case  in  the  anthracite 
region  generally,  as  well  as  in  some  of  the  rolling  mills  on  the 
Ohio  River.  In  some  cases,  the  waste  heat  is  conducted  in  flues 
under  the  steam  boiler ;  in  others,  the  steam  boiler  is  laid  on  the  top 
of  the  puddling  or  re-heating  furnace,  and  receives  the  heat  from 
the  flue  of  the  furnace  before  it  enters  the  stack.  Where  anthracite, 
which  is  not  easily  kindled,  is  burned,  the  waste  heat,  after  it  passes 
the  steam  boiler,  may  be  employed  in  heating,  to  a  limited  degree, 
the  alimentary  air  for  the  grate.  This  will  have  a  beneficial  effect, 
for  the  waste  heat  increases  the  temperature  of  the  furnace,  and 
occasions  a  direct  saving  of  about  ten  per  cent,  of  fuel ;  duly  esti- 
mating both  advantages,  the  saving  will  amount  to  at  least  twenty 
per  cent.  Heating  of  blooms,  and  bar,  or  sheet  iron,  by  means  of 
the  waste  flame  of  other  furnaces,  is  scarcely  worth  attempting,  for 
the  inconveniences  attending  this  practice,  added  to  the  loss  of  iron 
which  results,  may,  in  most  cases,  counterbalance  the  gain  in  fuel. 
Nevertheless,  where  both  skill  and  industry  have  been  brought  into 
requisition,  the  waste  heat  from  re-heating  furnaces  has,  in  some 
cases,  been  successfully  employed  in  heating  sheet  iron,  by  conduct- 
ing the  flame  over  a  layer  of  coke  or  charcoal.  The  waste  flame  of  the 
charcoal  forges  is  quite  bulky,  but  of  very  low  temperature  ;  it  can- 
not serve  with  advantage  for  any  other  purpose  than  the  heating  of 
pig  iron,  and  blast;  but  if  this  heating  is  well  managed,  twenty-five 


WASTE  HEAT  AND  GAS.  445 

to  thirty  per  cent,  of  coal  may  be  saved.  The  best  use  which  can 
be  made  of  this  flame  is  to  apply  it  in  the  generation  of  steam.  If 
the  attempts  which  have  been  made,  in  Eastern  Pennsylvania,  to 
construct  light  and  fast  working  steam  hammers  shall  ultimately 
prove  successful,  it  may  not  be  far  amiss  to  conjecture  that  the 
charcoal  fire  will  successfully  rival  the  puddling  furnace,  at  least 
in  those  cases  where  mineral  coal  commands  a  comparatively  high 
price. 

b.  The  waste  heat  of  the  blast  furnace  is,  as  we  have  stated,  im- 
mense; we  shall  not  greatly  err,  if  we  assert  that  150  pounds  of  coal 
are  used,  where  only  ten  pounds  are  actually  needed  to  produce 
that  amount  of  heat  and  gas  which  is  required  to  revive  and  melt 
a  given  quantity  of  iron.  Practical  investigations  on  a  small  scale 
have  shown  that  thirty  pounds  of  coal  are  sufficient  to  produce  100 
pounds  of  iron.  Be  this  as  it  may,  this  much  is  certain,  that  an 
immense  quantity  of  heat  is  wasted,  to  employ  which  various 
means  have  been  resorted  to.  One  of  the  most  common  appli- 
cations of  the  top  flame  was,  at  one  time,  to  the  burning  of  lime; 
for  this  purpose  it  is  excellently  adapted,  producing  a  fine  article. 
The  burning  of  lime  is  admissible  at  every  furnace  where  heat  is 
wasted;  apart  from  the  generation  of  steam,  nothing  is  so  well  cal- 
culated to  absorb  the  heat,  which  is  otherwise  of  no  use,  as  this  pro- 
cess. The  waste  heat  from  the  blast  furnace  has  also  been  em- 
ployed to  heat  the  blast ;  but  the  temperature  of  the  trunnel-head 
flame  is  so  high,  that  the  heating  apparatus  cannot  well  be  ap- 
plied directly  to  the  throat  of  the  furnace;  in  this  case,  the  con- 
ducting of  the  flame  under  a  steam  boiler,  before  it  enters  the  hot 
blast  stove,  is  a  preferable  arrangement.  In  some  establishments 
of  France  and  Germany,  though  not  in  this  country,  waste  heat  is 
employed  in  charring  wood,  stone  coal,  or  turf.  Such  an  applica- 
tion is  advantageous  where  the  products  of  distillation,  such  as 
pyroligneous  acid  and  coal  tar,  are  of  value.  But  this  is  the  case 
only  to  a  limited  degree  in  this  country.  The  charcoal  or  coke, 
which  is  then  made  in  iron  retorts,  is  inferior  to  kiln  charcoal;  and 
if  the  yield  were  as  great  in  kilns  as  in  these  retorts,  no  profit  would 
result  from  thus  making  charcoal,  unless  the  products  of  distillation 
were  worth  the  labor  spent  in  obtaining  them.  The  most  com- 
mon application  of  the  top  flame  is,  at  present,  to  the  generation  of 
steam  for  the  blast  machine ;  it  is  generally  applied  at  anthracite 
furnaces,  and,  in  a  great  measure,  at  charcoal  furnaces.  This  is  a 
highly  judicious  and  economical  application ;  it  facilitates,  in  a  great 


446  MANUFACTURE   OF  IRON. 

measure,  the  erection  of  furnaces,  and  at  places  where,  under  other 
circumstances,  no  furnace  could  be  erected.  An  attempt  has  been 
made  to  apply  the  trunnel-head  flame,  at  charcoal  and  some  of  the 
anthracite  furnaces,  to  the  roasting  of  ore.  "Where  the  waste  flame 
is  free  of  sulphur,  as  at  charcoal  furnaces,  this  application  may  be 
considered  the  best  use  which  can  be  made  of  it.  The  waste  flame 
from  bituminous  or  sulphurous  coal  would  not  be  of  service,  be- 
cause of  the  facility  with  which  it  would  carry  sulphur  into  the  ores. 
In  roasting  ores,  heat  of  a  low  degree,  steam,  and  carbonic  acid  are 
required.  This  is  exactly  the  composition  of  most  waste  flames, 
and  though  it  were  not,  they  can  be  easily  brought  to  that  composi- 
tion. From  the  top  of  the  blast  furnace,  the  heat  may  be  con- 
ducted through  brick  channels  to  the  yard,  and  discharged  into  the 
ore  piles. 

c.  We  repeat,  the  use  of  the  waste  flame  deserves  attention,  in  this 
country,  not  because  fuel  is  expensive — for  that  may  be  obtained  at 
a  reasonable  price  everywhere,  and  at  most  places  very  cheaply — but 
on  account  of  labor.  The  waste  flame  requires  no  attention,  after 
an  apparatus  for  employing  it  is  once  erected;  in  homely  language, 
it  is  a  fuel  which  requires  no  handling,  no  transport,  no  room— «and 
therefore  no  labor.  The  use  we  make  of  it  is  quite  significant ;  it 
serves  the  same  purpose  as  labor-saving  machines.  The  cases  in 
which  it  may  be  beneficially  applied  are  the  following :  In  burning 
lime  and  iron  ore,  in  generating  steam,  heating  hot  blast,  burning 
clay  for  firebrick,  heating  pig  iron  and  metal  for  the  forge  and  pud- 
dling furnace,  and  in  burning  brick  and  pottery  ware ;  in  fact,  in 
all  cases  in  which  a  large  body  of  heat,  though  not  a  high  heat,  is 
required.  For  the  manufacture  of  charcoal,  coke,  and  for  drying 
wood,  waste  heat  can  seldom  be  profitably  employed. 

II.  Gas. 

a.  Carbonic  oxide  gas  is  commonly  recognized  among  iron 
manufacturers  by  the  simple  term  gas.  Several  years  since,  it  was 
regarded  by  practical  and  scientific  men  with  profound  and  absorb- 
ing interest.  The  sensation  which  it  excited  has  measurably 
passed  away.  At  one  time,  indeed,  some  mysterious  power  was 
attributed  to  it;  some  vague  notions  were  entertained  concerning 
the  manner  in  which  it  saved  fuel ;  and  various  incomprehensible 
qualities  were  predicated  of  it. "  But  these  ideas  have  vanished 
from  the  public  mind,  and  the  advantages  of  gas  are,  at  the  pre- 
sent time,  placed  in  a  light  so  clear  that  every  one  may  appre- 


WASTE   HEAT  AND   GAS.  447 

ciate  and  understand  them.  Carbonic  oxide  gas  is  generated 
wherever  oxygen  or  air  is  conducted  through  a  column  of  coal  of 
greater  or  less  height.  As  explained  in  Chapters  II.  and  III.,  it  is  a 
combination  of  carbon  and  oxygen  ;  only  half  the  amount  of  oxy- 
gen is  contained  in  this  combination  which  is  required  to  give  the 
full  effect  of  combustion.  It  is,  therefore,  easily  understood,  that 
the  conversion  of  coal  into  carbonic  oxide  will  produce  only  half 
the  amount  of  heat  which  its  conversion  into  carbonic  acid  will 
produce  ;  because  the  amount  of  oxygen,  and  not  the  amount  of 
carbon  which  enters  into  combination,  determines  the  amount  of 
heat.  Consequently,  if,  in  making  carbonic  oxide,  the  heat  is 
raised  to  1000  degrees,  it  will  be  raised  an  additional  1000  degrees, 
by  adding  one  more  equivalent  of  oxygen.  These  are  the  princi- 
ples involved  in  this  question. 

If  we  consider  that,  by  no  possible  means,  can  a  higher  heat  be 
produced  by  the  combustion  of  carbon  than  that  generated  by  the 
conversion  of  the  carbon  into  carbonic  acid,  the  mystery  involved 
in  this  subject  may  be  easily  understood ;  and  we  shall  thus  see  that 
gas  effects  nothing  more  than  what  hot  air  produces,  namely,  tho- 
rough combustion.  The  advantages  derivable  from  double  combus- 
tion are  small  where  anthracite  coal  is  employed,  and  amount  to 
nothing  at  all  where  bituminous  coal  or  wood  is  burned.  The  tri- 
fling advantages  derived,  at  the  puddling  and  re-heating  furnaces, 
from  gas  and  anthracite  coal,  have  been  succeeded  by  disadvan- 
tages resulting  from  a  more  complicated  apparatus,  such  as  loss 
of  heat,  so  that,  at  the  present  time,  scarcely  any  one  thinks  of  gas. 
A  German  invention,  by  means  of  which  the  gases  tapped  from  the 
blast  furnace  could  be  employed  for  various  purposes,  originated 
this  application  of  gas  in  this  country.  Nearly  all  of  the  experi- 
ments which  have  been  made  relative  to  it  have  resulted  in  failure ; 
and  this  untoward  result  might  have  been  obviated,  in  a  great 
measure,  if  the  public  had  reflected  with  coolness  and  deliberation 
on  the  matter. 

b.  The  tapping  of  the  gas  from  the  blast  furnace  is  a  subject 
which  is  not  well  understood  by  many  of  our  manufacturers.  We 
shall,  therefore,  endeavor,  as  far  as  we  are  able,  to  remove  all  doubts 
concerning  it.  That  there  is  an  immense  waste  of  heat  at  a  blast 
furnace,  we  have  once  and  again  stated ;  and  it  is  very  natural  to 
endeavor  to  show  its  application.  The  gases  on  the  very  top  of  the 
furnace  are  more  impure  than  those  at  a  lower  point  in  the  furnace  ; 
they  are  moister,  and  contain  more  carbonic  acid.  Therefore,  they 


n 


448  MANUFACTURE   OF   IRON. 

cannot  generate  a  much  greater  amount  of  heat  than  they  already 
possess,  for,  in  the  chief  part  of  their  composition,  they  are  already 
oxidized  to  such  a  degree  that  they  cannot  absorb  and  combine  with 
much  more  oxygen  ;  consequently,  their  capacity  to  raise  tempera- 
ture is  very  limited.  The  great  difference  in  the  composition  of  the 
furnace  gases  taken  from  the  top,  and  those  taken  from  ten  feet 
below  the  top,  is  easily  explained,  if  we  take  into  consideration  the 
large  amount  of  water  and  gaseous  matter  the  fresh  ore  and  coal 
contain.  The  flame  at  the  top  contains,  in  the  form  of  very  hot 
steam,  all  the  water  which  the  fuel  and  the  ore  contained,  and  it 
is,  in  consequence,  of  a  low  temperature ;  it  also  contains  all  the 
gas  condensed  in  the  charcoal,  or  coke,  as  well  as  that  in  the  ore, 
and  a  part  of  the  carbonic  acid  gas  from  the  limestone.  For  these 
reasons,  this  flame,  containing  but  little  carbonic  oxide,  or  hydro- 
gen, the  only  combustible  elements,  cannot  generate  much  additional 
heat,  because  it  has  very  small  capacity  for  oxygen.  Another  reason 
why  the  top  flame  cannot  generate  intense  heat,  is  obvious.  If  the 
oxidation  of  carbon  is  carried  so  far  as  to  produce  carbonic  oxide,  the 
temperature  cannot  be  more  than  half  that  of  carbonic  acid.  There 
is  a  slight  difference ;  but  this,  in  our  case,  can  be  neglected. 
Should,  therefore,  the  degree  of  heat  evolved  in  making  carbonic 
acid  be  2000°,  (it  is,  in  fact,  greater,  but  we  assume  a  round  num- 
ber for  the  sake  of  simplicity,)  a  temperature  of  1000°  will  result 
from  making  carbonic  oxide.  If  carbonic  oxide  of  1000°  is  brought 
in  contact  with  oxygen,  or  atmospheric  air,  under  favorable  circum- 
stances, the  union  will  produce  a  temperature  of  2000°.  But  it  can- 
not, under  any  conditions,  produce  any  degree  beyond  a  limited 
maximum.  If  the  conditions  of  combustion  are  unfavorable,  that 
is,  if  the  carbonic  oxide  gas  is  of  a  lower  temperature  than  1000°, 
and  the  atmospheric  air  is  colder  tHan  32°,  the  degree  of  heat 
evolved  in  combustion  will  be  considerably  less ;  so  much  so  that, 
if  the  carbonic  oxide  is  only  32°,  and  the  air  32°,  the  highest  heat 
resulting  from  their  union  would  be  only  1000° ;  in  practice,  in- 
deed, it  would  fall  far  short  of  that  degree. 

This  statement  will  give  us  a  correct  idea  of  the  operation  of  gas, 
from  blast  as  well  as  other  furnaces.  If  the  gas,  on  being  con- 
ducted from  the  place  of  generation  to  that  of  combustion,  loses  any 
of  its  heat,  that  heat  is  lost  in  combustion.  As  we  are  aware  that 
it  is  almost  impossible  to  conduct  heated  gases  without  loss  of  heat, 
we  may  expect  that  the  degree  of  heat  evolved  during  the  combus- 
tion of  gaseous  combustibles  can  in  no  instance  be  so  high  as  that 


WASTE   HEAT  AND   GAS.  449 

resulting  from  the  direct  combustion  of  the  fuel,  when  converting 
it  into  carbonic  acid.  This  evil  can,  in  some  measure,  be  obviated 
by  employing  heated  air  in  the  generation  of  the  gas  as  well  as 
in  the  final  combustion.  But  so  complicated  are  the  arrangements 
by  which  such  results  are  effected,  that  the  fuel  economized  would 
not  compensate  the  iron  manufacturer  for  their  use.  If  the  carbonic 
oxide  gas  is  cold,  or  comparatively  cold,  and  the  atmospheric  air 
is  also  cold,  still  more  serious  losses  of  heat  take  place  ;  for,  in  this 
case,  the  combustion  is  very  imperfect,  and  air  and  gas  may  mingle 
without  chemical  combination,  when,  of  course,  they  will  not  gene- 
rate heat  at  all. 

The  top  gases  of  a  blast  furnace  cannot  generate  a  maximum  of 
heat,  because  they  are  necessitated  to  pass  through  a  column  of 
cold  material.  In  the  generation  of  carbonic  oxide  gas,  a  cherry- 
red  heat  is  produced.  A  degree  of  heat  in  the  carbonic  oxide  gas 
sufficient  to  heat  any  solid  substance  to  such  a  redness,  without 
coming  in  contact  with  oxygen,  is  indispensable.  Otherwise,  we 
cannot  expect  a  corresponding  high  heat  in  the  ensuing  combus- 
tion, that  is,  in  the  formation  of  carbonic  acid.  Now  we  know  that 
if  hot  gas  is  conducted  in  iron  pipes,  it  loses  a  large  quantity  of 
heat;  even  in  brick  channels,  a  large  amount  is  lost  by  radia- 
tion. Such  gas  will  never  produce  heat  equal  in  quality  and  quan- 
tity to  that  produced  by  direct  combustion.  In  a  blast  furnace, 
the  gases  cannot  be  of  the  highest  degree  of  temperature,  because 
the  interior  surface  of  the  furnace  is  so  large  that  a  large  quantity 
of  heat  is  lost  by  radiation  and  contact.  Such  gas  may  be  tapped 
as  low  in  the  stack  as  we  choose.  If  conducted  in  iron  pipes,  it 
loses  still  more  heat,  and  often  arrives  at  the  place  of  combustion 
not  even  sufficiently  warm  to  melt  lead.  It  is  said  that  iron  melts  at 
a  temperature  between  2500°  and  3000°  Fahr. ;  and  that  the  high- 
est degree  of  heat  which  can  be  generated  by  carbon,  in  its  trans- 
formation into  carbonic  acid,  is  4000°.  Cold  carbonic  oxide  could 
not  generate  a  degree  of  heat  beyond  2000°,  and  if  sufficiently 
warm  to  melt  lead,  about  500°,  it  will  generate  in  its  final  com- 
bustion a  temperature  of  2500°,  which  is  barely  sufficient  to  melt 
the  most  fusible  iron,  and  not  sufficient  for  welding  any  kind  of 
iron.  This  result,  which  might  have  been  .deduced,  twenty  years 
ago,  from  certain  fundamental  principles,  was  not  confirmed  by 
practice  until  after  many  fruitless  experiments,  much  loss  of  time, 
and  large  expenditure  of  means. 

We  may,  from  these  considerations,  infer  that  the  generation 
29 


450 


MANUFACTURE   OF  IRON. 


of  carbonic  oxide  gas,  subservient  to  a  final  combustion,  occasions 
loss  rather  than  gain.  "VYe  may  now  consider  this  an  established 
principle.  Though  a  few  exceptions  to  this  rule  exist,  attributable 
to  local  causes — for  example,  those  instances  in  which  fine  coal  or 
sawdust  is  the  fuel  employed — they  do  not  invalidate  our  conclusion. 
So  long  as  we  cannot  convert  quantitative  heat  into  qualitative  heat, 
the  advantages  which  gas  are  assumed  to  possess  are  chimerical. 

The  gas,  which  is  tapped  from  a  blast  furnace  interferes  more  or 
less  with  its  operations,  at  least  if  it  is  tapped  in  large  quantity,  and 
taken  from  a  low  point  in  the  furnace  stack.  For  these  reasons, 
we  should  avoid  tapping  it  low.  The  temperature  of  this  gas  is  not 
sufficiently  high  to  make  it  of  use  in  puddling  or  re-heating  opera- 
tions. It  makes  very  little  difference  whether  the  gas  is  taken  di- 
rectly from  the  top,  or  from  a  point  slightly  below  the  top. 

At  the  charcoal  furnace,  upon  the  top  of  which  there  is  a  chimney 
that  can  be  shut  or  opened  by  means  of  a  damper,  it  is  preferable 
to  take  the  gas  from  the  very  top ;  but  at  the  coke  or  anthracite  fur- 
nace, the  large  throat  of  which  makes  a  chimney  impracticable,  it 
is  advisable  to  tap  the  gas  for  the  steam  boilers  and  hot  air  appa- 
ratus a  few  feet  below  the  top,  so  that  the  pressure  of  the  blast  may 
assist  in  driving  the  gas  under  the  boilers.  Fig.  147  exhibits 

Fig.  147. 


Tapping  the  gas  from  below  the  top. 

such  an  arrangement.     The  gas,  which  is  taken  from  a  point  three 


WASTE  HEAT  AND  GAS.  451 

or  four  feet  below  the  top  of  the  furnace,  is  conducted  by  six  or 
more  holes  (flues)  into  a  kind  of  receiver  a,  #,  which  gathers  the  gas, 
and  conducts  it  to  the  steam  boiler,  or  to  any  appropriate  place. 
This  receiver  runs  all  around  the  air-wall  of  the  furnace ;  the  flues 
and  the  receiver  should  be  made  of  fire  brick,  and  well  secured. 
From  the  steam  boilers  the  gas  is  conducted  into  the  heating  stove, 
for  the  purpose  of  heating  the  blast,  and  thence  into  the  chimney, 
from  thirty  to  fifty  feet  in  height.  This  arrangement  is  generally 
adopted  at  the  anthracite  furnaces. 

If  practical  experiments  with  gas  have  not  resulted  in  those  ad- 
vantages which  were  at  one  time  supposed  to  be  derivable  from  its 
use,  they  have  at  least  had  the  effect  of  drawing  the  attention  of 
the  public  mind  to  the  nature  of  combustion.  Still,  notwithstand- 
ing the  comparatively  extended  knowledge  of  the  sources  of  heat 
which  we  have  obtained  from  a  rigid  investigation  of  this  interest- 
ing subject,  we  are  not  at  all  disposed  to  regard  the  questions  it 
involves  as  exhausted.  By  means  of  patience,  skill,  and  science, 
hot  air  and  gas  may  yet  prove  to  possess  advantages  of  which,  in 
our  present  state  of  knowledge,  we  are  ignorant.  But  we  have  no 
reason  to  suppose  that  these  will  ever  possess  a  mysterious  import- 
ance like  that  attributed  to  them,  several  years  since,  by  imagina- 
tive minds. 


452  MANUFACTURE  OF  IRON. 


CHAPTER   IX. 

FIRE  BRICK  AND  REFRACTORY  STONES. 

Or  the  fusibility  and  refractory  qualities  of  matter,  we  have  al- 
ready spoken  at  great  length  in  Chapters  III.  and  IV.;  but  we 
wish  to  be  more  specific  with  reference  to  certain  refractory  elements 
and  compounds. 

In  this  work,  the  terms  refractory  or  fire-proof  are  used  in  quite 
a  relative  sense ;  if  all  matter  which  resists  heat  should  be  considered 
refractory,  we  would  experience  but  little  difficulty  in  making  fire- 
proof brick  or  stones.  It  is  not  heat  which  destroys  our  furnace 
hearth  or  lining;  it  is  not  the  intensity,  the  quality,  of  caloric 
which  melts  fire  bricks.  The  chemical  affinity  of  the  matter  which 
we  melt  in  an  apparatus  for  the  matter  of  which  the  apparatus  is 
constructed  is  that  which  is  most  effective  in  destroying  refractory 
material.  Both  silex  and  alumina  are  infusible,  whether  single 
or  combined;  but,  if  combined  with  potash  or  soda,  they  may  be 
melted  over  a  spirit-lamp.  Lime,  magnesia,  and  baryta  form  more 
or  less  fusible  compounds  with  silex  or  clay,  but  cannot  be  fused  to- 
gether with  pure  potash  or  soda.  The  oxides  of  iron  or  manganese 
melt  readily  together  with  silex  and  alumina,  but  not  with  pure 
potash  or  pure  soda.  These  are  the  principles  by  which  we  must  be 
governed,  in  our  efforts  to  make  a  refractory  material.  It  is  evident 
from  this,  that,  if  we  heat  potash,  soda,  lime,  and  magnesia,  in  con- 
tact with  silex,  the  latter  will  be  dissolved,  in  proportion  to  the 
quantity  of  the  potash,  to  the  intensity  of  the  heat,  and  to  the  length 
of  time  it  was  exposed  to  the  heat.  If  the  amount  of  potash  is  small, 
a  proportionally  less  amount  of  silex  will  be  dissolved;  for  it  is  a 
well-established  law  of  chemistry,  that  affinity  increases  with  the 
predominating  element.  Time,  and  intensity  of  heat  may  be  consi- 
dered two  agencies  possessing  similar  qualities.  What  time  cannot 
accomplish,  heat  will  effect.  Whatever  deficiency  exists  in  heat  can 
be  supplied  by  time.  The  oxides  of  iron  and  manganese  act  of 
course  like  potash. 


FIRE  BRICK  AND  REFRACTORY  STONES.  453 

The  most  refractory  matters  at  our  disposal  are  silex,  clay,  mag- 
nesia, lime,  and  baryta,  and  the  silicates  of  these  four  alkalies.  The 
most  refractory  are  the  silicates  of  alumina ;  next  in  order  are  the 
silicates  of  magnesia,  lime,  and  baryta.  Common  fire-clay  generally 
ranks  as  the  first,  soapstone  second,  and  impure  lime  the  third.  We 
should  carefully  bear  in  mind  what  has  been  said  in  Chapter  III., 
that  any  mixture  containing  more  than  two  elements  is  more  fusible 
than  a  compound  contaiDing  only  two;  that  is  to  say,  with  the  in- 
crease of  elements,  the  fusibility  increases. 

I.  Native  Refractory  Stones. 

Native  refractory  materials  are  sandstone,  clay  slate,  soapstone, 
mica  slate,  gneiss,  and  granite.  These  minerals  are,  however,  to  a 
certain  extent,  compounds  of  various  substances.  It  is,  therefore, 
necessary  to  select  them  with  care.  Sandstone  frequently  contains 
iron,  or  lime,  which,  according  to  the  degree  in  which  they  are  pre- 
sent, augment  or  diminish  its  fusibility.  The  admixture  can  seldom 
be  found  by  testing  with  acids  ;  fire  is  our  only  reliance.  What  we 
have  said  of  sandstone  is  applicable  to  all  the  other  native  materials. 

a.  Sandstone  is  quite  abundant  in  this  country,  and  is  extensively 
employed.    It  forms  the  cheapest  of  all  fire-proof  materials,  because, 
in  addition  to  its  abundance,  and  the  facility  with  which  it  can  be 
worked,  it  is  less  liable  to  melt  and  crack  than  any  other  native  ma- 
terial.    The  coarsest  kinds  are  the  best,  if  they  contain  sufficient 
cement  to  keep  them  together.     Certain  fine-grained  stones  are  ex- 
cellent ;  but  it  is  necessary  to  select  them.    The  red  sandstone,  of  the 
transition  series,  is  generally  good,  as  well  as  the  millstone  grit  be- 
neath the  bituminous  coal.     So  great  is  the  variety  of  sandstone  in 
the  western  coal  fields,  that  great  care  in  selection  is  required.    Less 
difficulty  is  experienced  in  the  anthracite  region.     Connecticut  con- 
tains a  most  beautiful  kaolin,  in  a  solid,  stone-like  form. 

b.  Clay-slate  and  shales  serve,  in  many  cases,  for  fire  brick.    These 
materials,  which  are  very  much  distributed  over  the  United  States, 
are  generally  more  fusible  than  sandstones  ;  but  they  are  preferable 
for  those  parts  that  are  liable  to  sudden  changes  of  heat ;  such,  for 
instance,  as  the  lining  and  top  of  blast  furnaces,  hot  blast  stoves, 
steam-boilers  and  flues,  roast  ovens,  and  limekilns.     In  such  cases, 
neither  high  heat  nor  chemical  action  is  to  be  expected.     Slates  and 
shales  may  be  found  in  abundance  in  the  coal  regions ;  and  by  a 
little  attention  to  color  and  grain,  we  shall  soon  be  able  to  detect  the 
best  kind. 


454  MANUFACTURE   OF  IRON. 

c.  Talc-slate,  or  soapstone,  is  very  refractory,  but  its  brittleness 
impairs  its  utility  as  a  fire-proof  material.  It  is  found  abundantly  in 
New  Jersey,  and  in  Eastern  Pa.,  as  well  as  in  several  other  States. 
It  is  employed  as  refractory  matter  in  puddling  furnaces,  as  men- 
tioned in  Chapter  IV.,  but  very  seldom  for  any  other  purpose.  None 
of  the  other  kinds  of  native  material,  with  the  exception  of  fire-clay, 
are  used  in  this  country.  In  fact,  those  we  have  described,  in  ad- 
dition to  being  preferable  to  any  others,  are  found  in  such  abun- 
dance as  to  render  the  employment  of  others  unnecessary. 

II.  Artificial  Refractory  Stones. 

Silex,  clay,  and  lime  are,  in  their  pure  state,  perfectly  infusible 
in  any  heat  which  we  can  possibly  produce.  But  we  do  not  class 
these  among  the  refractory  materials,  because  they  possess  no  ad- 
hesive properties,  and  cannot  be  brought  to  any  compact  form ; 
they  always  form  a  friable  mass,  which  will  be  destroyed  by  the 
rubbing  of  fuel  and  tools  against  it.  Therefore,  the  chemical  nature 
and  composition  of  a  material  are  not  the  only  qualities  which  ren- 
der it  fire-proof;  an  indispensable  element  is  its  mechanical  form. 
Burnt  lime,  perfectly  infusible  in  any  heat,  would  not  serve  the 
same  purpose  as  fire  brick,  because  of  its  friability.  Lime,  prepared 
under  the  heaviest  pressure  of  a  hydraulic  press,  is  scarcely  strong 
enough  to  resist  the  gentle  pressure  of  the  oxygen-hydrogen  flame 
of  the  Drummond  light ;  it  is  not  melted  in  this  flame,  but  destroyed 
by  the  velocity  of  the  atoms  of  the  gas.  The  same  is  the  case 
with  pure  silex  or  clay ;  when  both  are  mixed  together,  a  strong 
heat  is  required  to  form  a  kind  of  connection.  All  native  material 
contains  more  or  less  water,  which  makes  it  liable  to  destruction  by 
heat.  Of  all  such  materials,  silex  is  the  purest ;  next  to  this  is  clay. 
Clay  always  contains  a  large  amount  of  water,  which  it  retains  with 
obstinate  pertinacity ;  nor  will  a  cherry-red  heat  expel  it,  unless  that 
heat  is  of  long  duration.  Water,  however,  will  tend  to  make  the 
clay  porous,  and  thus  diminish  its  utility  as  a  refractory  material. 
All  our  fire-clays,  which  are  of  good  quality,  and  exist  abundantly  in 
the  United  States,  are,  if  free  of  other  matter,  a  composition  of  silex 
and  clay. 

a.  Fire  brick  may  be  made  like  ordinary  brick,  with  this  differ- 
ence, that  the  clay  should  be  properly  prepared  previous  to  mould- 
ing it.  Fire  brick  is  frequently  baked  in  a  kind  of  oven  different 
from  that  employed  for  burning  common  brick ;  but  this  is  a  mat- 
ter of  expediency  and  economy,  and  has  no  influence  upon  the  qua- 


FIRE  BRICK  AND  REFRACTORY  STONES.  455 

lity  of  the  fire  brick.  The  clay  used  for  this  purpose  may  be  tested 
by  exposing  a  small  piece  of  it,  for  an  hour  or  two,  to  the  strongest 
heat  of  a  blacksmith's  forge :  if  it  retains  its  white  color,  and  does 
not  become  glazed,  it  may  bo  considered  fire-proof.  There  are  two 
kinds  of  fire-clay  ;  the  one  is  solid,  of  a  stony  form,  or  like  shale  ; 
the  other  soft,  plastic.  The  first  is  found  almost  exclusively  in  the 
coal  series ;  the  second  in  all  kinds  of  geological  deposits,  from  the 
'  granite  to  the  alluvial  soil.  The  first  is  ground  under  iron  edge- 
wheels,  driven  by  a  steam-engine  or  horse  power,  and  it  can  also  be 
pounded  by  means  of  stamp  mills.  It  is  frequently  formed  directly 
into  brick  and  burnt ;  but  in  this  case  it  does  not  make  so  good  a 
brick  as  when,  after  the  first  grinding,  it  is  treated  like  plastic  clay. 
Plastic  clay  should  be  well  mixed  in  a  horse  mill,  similar  to  a  com- 
mon clay  mill,  formed  into  bricks  or  lumps,  and  then  burnt  by  as 
high  a  heat  as  that  applied  in  the  final  burning  of  the  brick.  This 
heat  expels  nearly  all  of  the  water  from  the  clay,  but  hardly  glazes  it. 
After  this,  the  clay  is  ground  or  pounded,  and  mixed  with  a  sufficient 
quantity  of  fresh  clay  to  make  it  adhere  together.  Bricks  are  then 
moulded  from  it,  and  burnt.  A  good  fire  brick  appears  white, 
almost  pure  white,  sometimes  with  a  flesh-colored  or  gray  tint.  It 
ought  to  be  slightly  glazed,  like  good  porcelain.  The  greater  its 
specific  gravity,  the  greater  will  be  its  durability. 

Fire  brick  ought  to  be  as  close  in  the  grain  as  possible.  If  the 
bricks  are  employed  only  in  re-heating  furnaces,  in  the  roofs  and  fire 
chambers  of  puddling  furnaces,  in  chimneys  in  the  lining  of  a  blast 
furnace,  or  in  air-stoves,  closeness  of  grain  is  not  of  much  import- 
ance ;  but  with  respect  to  the  lining  of  the  hearth  of  a  puddling 
furnace,  and  the  hearth  or  boshes  of  a  blast  furnace,  it  is  of  the 
first  consequence.  An  open,  porous  fire  brick,  or,  in  fact,  any  por- 
ous material  which  serves  for  that  purpose,  is  very  soon  destroyed  ; 
the  pores  multiply  the  surface.  The  same  relation  exists  between 
a  close  and  a  porous  brick  that  exists  between  powdered  material 
and  solid  matter.  In  such  a  condition,  chemical  solution  of  its  parts 
is  facilitated.  Therefore,  fire  brick  employed  in  places  where  even 
the  least  destruction  by  chemical  action  is  to  be  expected,  ought,  in 
addition  to  being  glazed,  to  exhibit  as  close  a  grain  as  possible,  as 
well  as  to  possess  great  specific  gravity.  The  lining  of  a  puddling 
furnace  with  fire  brick  would  be  accompanied  with  great  advantages ; 
but  every  attempt  to  secure  this  result  will  fail,  until  fire  brick  of 
proper  quality  are  used.  The  addition  of  carbon,  coke  dust,  and 
plumbago  to  fire-proof  admixtures  increases  the  fusibility  of  the 


456  MANUFACTURE   OF   IRON. 

brick,  and,  besides  weakening,  exerts  an  injurious  influence  in  the 
puddling  furnace.  Plumbago  is  frequently  mixed  with  fire-clay  in 
making  crucibles.  It  is  added,  not  for  the  purpose  of  enabling  the 
crucible  to  resist  a  higher  heat,  but  for  the  purpose  of  preventing  it 
from  breaking,  when  suddenly  cooled  and  heated.  Such  a  crucible 
does  not  resist  as  much  heat  as  one  made  of  silicious  matter ;  but 
the  latter  is  very  liable  to  break  during  or  after  the  first  heat. 
The  plumbago  crucible,  if  well  made,  will  endure  ten  or  twelve 
heats  in  melting  iron. 

b.  Artificial  sandstone  is  an  article  very  little  used  in  this  coun- 
try ;  but  as  cases  may  occur  in  which  it  can  be  of  service,  we  shall 
devote  a  short  space  to  its  consideration.  At  many  establishments 
on  the  Continent  of  Europe,  artificial  sandstones  are  used  instead  of 
fire  brick,  and,  strange  as  it  may  appear,  they  are  used  for  hearth 
and  boshes  in  blast  furnaces.  They  can  be  made  from  any  good, 
coarse,  silicious  sand,  which  does  not  melt  in  a  high  heat.  Sand 
generally  contains  some  foreign  matter,  particularly  lime,  of  which 
even  river  sand  is  not  free.  Such  matter  must  be  removed.  The 
surest  method  of  procedure  is,  in  all  cases,  to  burn  the  sand,  peb- 
bles, or  native  sandstone,  in  a  cherry-red  heat ;  the  lime,  which  it 
may  contain  as  a  carbonate,  may  thus  be  burnt,  when  it  can  be 
removed  by  pounding  and  washing.  In  large  iron  manufactories, 
this  branch  of  the  business  is  quite  an  extensive  one,  and  the  mills 
for  pounding  and  grinding  receive  considerable  attention.  Where 
coarse  pure  sand  cannot  be  obtained,  which  is  frequently  the  case, 
particularly  in  the  coal  regions,  silicious  or  white  river  pebbles  may 
be  employed ;  or,  if  these  cannot  be  had,  white  coarse  sandstone, 
or  millstone  grit.  This  is  burnt,  pounded,  and  washed.  The  arti- 
ficial sand,  thus  derived  from  pebbles  or  stone,  is  mixed  with  about 
one-fourth  or  one-sixth  of  its  amount  of  fire-clay,  or  with  just  a  suf- 
ficient quantity  to  keep  the  mass  together  after  being  dried.  The 
finer  the  sand  has  been  pounded,  and  the  more  tenacious  the  clay, 
the  less  of  the  latter  which  will  be  required.  Before  the  clay  is 
mixed  with  the  sand,  it  is  burnt  and  pounded.  '  Clay  should  be 
burnt,  under  all  conditions,  for  raw  clay  contains  a  large  amount 
of  water.  If  once  burnt,  it  will  not  absorb  so  much  moisture  as  it 
previously  contained.  If  fire  brick  is  made  from  clay  containing  a 
large  amount  of  water,  or  from  green  clay,  it  will  be  porous;  for 
the  water  which  is  evaporated  from  the  interior  of  the  brick  of 
course  occupied  a  certain  space.  If  the  pounded  sand  is  too  coarse, 
or  if  the  grains  are  round,  spaces  will  be  left  between  them,  to  fill 


FIRE  BRICK  AND  REFRACTORY  STONES.  457 

which  a  large  amount  of  clay  will  be  required ;  in  sach  a  case,  the 
stone  will  not  glaze  well,  when  exposed  to  heat.  Therefore,  the 
artificial  sand  and  burnt  clay  are  moistened  with  as  little  water 
as  possible,  and  mixed  together  thoroughly ;  the  latter  object  may 
be  best  effected  by  means  of  edge-wheels.  The  damp  mass  is 
formed  into  bricks  in  the  common  way.  These  bricks  may  have 
any  form  most  conveniently  adapted  for  our  purposes.  In  rolling 
mills,  specific  forms  are  desirable  for  the  various  corners,  angles, 
and  arches  of  the  puddling  and  re-heating  furnaces.  After  being 
stored  under  an  open  shed,  and  air-dried,  they  are  ready  for  use. 
It  would  be  a  vain  attempt  to  burn  such  an  artificial  sandstone, 
for  the  highest  heat  of  the  re-heating  furnace  would  scarcely  glaze 
it,  if  the  iron  did  not  form  an  alkali ;  by  this  means,  a  glazing  at 
the  surface  of  the  interior  is  effected.  Such  stones,  if  not  cheap  at 
first  cost,  are  easily  cut,  easily  laid,  easily  removed,  and  no  loss 
arises  from  spales  or  bats,  for  any  unglazed  remains  of  the  stone 
are  easily  transformed  into  new  brick  again.  However  useful  a 
material  in  the  rolling  mill,  they  are  less  adapted  for  the  fire-place, 
and  the  lining  of  the  hearth  of  a  puddling  furnace.  The  least  touch 
with  an  iron  tool  will  destroy  them;  but  where  no  mechanical  or 
chemical  action  is  exercised,  they  are  equal,  if  not  preferable  to 
the  best  fire  brick. 

Of  such  artificial  sandstones,  the  hearth  and  boshes  of  blast  fur- 
naces are  built,  and  are  said  to  a'nswer  well.  If  the  raw  material 
has  been  carefully  managed,  the  statement  may  be  true.  We  know 
that,  in  the  coke  blast  furnace  of  Silesia,  a  similar  mass  is  used, 
which  is  pounded  in  moist;  the  hearth  forms  a  single  sandstone. 
This  kind  of  hearth  is  very  durable,  and  commonly  endures  a  blast 
of  twenty-four  months,  and  occasionally  a  blast  even  of  four  or  five 
years.  In  the  preparation  of  the  mass,  less  reliance  can  be  placed 
on  its  composition  than  upon  the  careful  mixing  of  the  compound. 
Air-dried  stones  may  be  made  of  pure  fire-clay ;  but  these  are  not 
so  durable  as  the  sandstones  of  which  we  speak.  These,  as  we 
have  stated,  ought  never  to  be  made  of  green  clay,  even  if  the  clay 
is  of  the  best  quality.  Clay  and  silex,  be  it  observed  once  for 
all,  are  the  only  serviceable  materials  for  fire-proof  stones. 

c.  The  joints  of  fire  brick,  sandstones,  and  artificial  stones  are 
to  be  thoroughly  filled  by  mortar.  The  mortar  ought  to  form  a  kind 
of  solder  between  one  stone  and  another,  and  may,  for  this  reason, 
be  more  fusible  than  the  bricks  or  stones  themselves.  Pure  fire-clay 
is  not  a  good  mortar,  for  it  cracks  in  drying,  and  leaves  spaces, 


458  MANUFACTURE  OF  IRON. 

•which  occasion  the  destruction  of  the  stone.  A  mixture  of  fire- 
clay and  fine  sand  is  preferable,  not  because  it  does  not  melt,  but 
because  it  shrinks  less  in  drying.  The  very  best  mortar  for  hearth- 
stones and  fire-brick  is  made  of  a  mixture  of  fire-clay  and  finely 
pounded  blast  furnace  cinder;  this  mortar  will  cement  stones  and 
bricks  firmly. 

III.   Conductors  of  Heat. 

In  concluding  this  chapter,  we  shall  make  a  few  remarks  on  the 
capacity  of  matter  to  conduct  and  reflect  heat,  so  far  as  this  subject 
has  any  relation  to  the  object  of  our  work.  Metals  are  the  best  con- 
ductors and  reflectors  of  heat;  therefore,  for  its  preservation  iron  or 
copper  pipes  are  evidently  unserviceable.  To  conduct  hot  air  in 
iron  pipes  is  a  violation  of  established  principles,  but,  unfortunately, 
we  cannot  substitute  for  such  metal  any  material  of  less  conducting 
power;  the  same  remark  is  applicable  to  steam-conducting  pipes. 
A  boiler  of  fire-clay  would  be  useless;  for,  in  addition  to  its  weak- 
ness, a  great  deal  of  fuel  would  be  required  to  raise  steam  in  it. 
This  applies  equally  well  to  air-heating  pipes.  An  iron  roof  on  a 
puddling  furnace  would  not  answer,  even  though  the  iron  should 
not  melt;  for  the  furnace  would  not  retain  sufficient  heat  to  work 
the  iron  it  contains.  It  is  a  good  arrangement  to  place  pipes  ver- 
tically, if  we  desire  to  retain  the  heat ;  but  if  we  wish  to  conduct  it, 
by  the  medium  of  the  pipe,  from  the  fire  to  the  interior  of  the  pipe 
— an  object  we  seek  to  secure  by  employing  heating  apparatus  and 
steam  boilers — it  is  entirely  wrong  thus  to  place  them.  In  these  cases, 
heat  is  conducted  by  contact,  and  by  the  motion  of  gases;  for  this 
reason,  we  should  employ  the  best  conductors  of  heat,  and  put  these 
in  such  a  position  as  to  offer  the  largest  surface  to  the  moving  gases. 
We  may  consider  this  surface  extended,  if  the  heated  particles  of 
air  can  change  position  among  themselves.  This  object  may  be 
effected  by  exposing  a  convex  surface  to  the  current  of  the  hot  gases. 

The  reflective  capacity  of  matter  depends,  in  some  measure,  on 
color  and  polish.  A  bright  surface  will  reverberate  more  heat  than 
a  dull  surface.  This  fact  we  may  observe  in  a  new  puddling  or  re- 
heating furnace,  for  a  furnace  with  an  unglazed  roof  cannot  be  well 
heated.  No  furnace  works  well  until  its  whole  interior  surface  is 
glazed.  If  it  were  not  possible  to  glaze  fire  brick,  the  strongest  heat 
would  not  make  a  furnace  sufficiently  warm  for  puddling  or  heating. 
A  roof  of  carbon,  black  and  velvety,  would  not  heat  a  puddling 
furnace  red  hot ;  from  whic*h  we  may  infer  that  white  fire  brick  or 


FIRE  BRICK  AND  REFRACTORY  STONES.  459 

stones  produce  a  higher  temperature  at  those  points  accessible  to 
their  reflected  heat  than  brick  or  stones,  which  are  of  a  dark  color. 
From  this,  we  may  easily  understand  why  a  furnace  hearth  gets 
cold — unaccountably  to  him  who  does  not  bear  in  mind  the  fact — 
when  we  smelt  black  cinder  in  the  blast  furnace,  and  why  an  excess 
of  limestones  or  gray  cinders  draws  the  heat  into  the  hearth.  Other 
circumstances  being  equal,  the  heat  will  be  greatest  at  those  points 
which  exhibit  the  brightest  color,  or  polish,  and  at  a  concave  sur- 
face whence  the  reflected  rays  of  light  are  thrown  into  a  focus. 
With  the  latter  part  of  this  theory  all  are  practically  acquainted 
who  understand  the  nature  of  the  lens. 

From  these  important  considerations,  we  conclude  that  dark  fire- 
proof stones  are  an  unserviceable  material ;  that  a  glazing  of  the 
stones  and  fire  brick  is  essentially  necessary,  particularly  in  the 
fire-chambers  and  hearths  of  the  puddling,  re-heating,  and  blast 
furnaces ;  that  the  roof  and  bottom  of  a  puddling  furnace  ought  to 
form  the  two  surfaces  of  a  lens,  so  as  to  throw  the  highest  heat 
above  the  bottom,  and  between  the  bottom  and  roof;  and  that  the 
roof  of  a  re-heating  furnace  should  be  as  straight  as  possible,  so  as 
to  produce  a  uniform  heat  over  the  entire  bottom.  By  reference 
to  these  laws  of  physics,  we  are  able  to  understand  the  influence 
exerted  by  steep  boshes  in  a  blast  furnace,  and  to  know  where  the 
heat  is  thrown,  when  the  boshes  are  drawn  from  the  widest  part  of 
the  furnace  down  to  the  tuyere ;  this  is  frequently  done,  and  an- 
swers an  excellent  purpose.  A  greatly  tapered  hearth  will  throw 
the  highest  heat  above  the  tuyere,  while  a  cylindrical  hearth  will 
retain  it  just  at  the  tuyere.  From  this,  we  may  understand  that 
a  furnace  whose  hearth  is  injured  does  not  work  well;  for,  in 
that  case,  particularly  where  there  are  more  tuyeres  than  one,  a 
lens  is  formed  by  the  concavities  of  the  tuyeres,  and  the  highest 
heat  of  the  furnace  is  thrown  below  them,  at  which  point  it  has  the 
effect  of  reducing  cinder  and  impurities  along  with  the  iron.  These 
observations  enable  us  to  understand  why  ores  of  a  refractory  na- 
ture do  not  work  well  in  a  narrow  hearth,  and  why  fusible  ores 
work  most  profitably  in  a  high  cylindrical  hearth  and  flat  boshes. 
In  the  former  case,  we  require  a  high  preparatory  heat  in  the 
stack ;  in  the  latter,  a  very  low  heat. 


460  MANUFACTURE    OF   IRON. 


CHAPTER  X. 

MOTIVE  POWER. 

THE  consideration  of  this  subject  belongs  to  those  works  which 
treat  specifically  of  mechanical  science ;  still,  as  motive  power  is 
extensively  applied  in  iron  manufactories,  a  few  remarks  in  rela- 
tion to  it  may  not  be  without  interest  and  profit. 

Lack  of  power  is  one  of  the  worst  evils  to  which  an  iron  factory 
can  be  exposed.  If  power  is  deficient,  nothing  works  rightly ;  every- 
thing is  in  disorder.  Sometimes  we  are  compelled  to  modify  opera- 
tions, and  reconstruct  apparatus,  where  it  does  not  bear  a  certain 
relation  to  the  engine  or  the  waterwheel.  The  amount  of  power 
necessary  for  the  different  branches  of  the  business  varies  accord- 
ing to  circumstances.  Where  the  blast  machines  are  well  con- 
structed, a  power  of  sixteen  horses  is  required  at  a  charcoal  furnace, 
a  power  of  forty  at  a  coke  furnace,  and  a  power  of  sixty  at  an  an- 
thracite furnace.  By  means  of  the  latter  power,  applied  in  a  rolling 
mill,  with  squeezers,  we  ought  to  produce  100  tons  of  small  and 
coarse  rod,  and  hoop  iron,  or  200  tons  of  rails  and  heavy  bar,  per 
week.  A  sheet  iron  factory  is  never  profitable  if  it  lacks  motive 
power ;  in  fact,  the  profits  of  such  an  establishment  chiefly  depend 
upon  its  successful  application.  The  power  exerted  by  a  water- 
wheel  cannot  be  calculated  except  by  means  of  a  dynamometer ; 
we  refer  to  those  who  are  interested  in  this  subject  to  works  on  hy- 
draulics, whence  they  can  obtain  all  necessary  information.  Water- 
wheels  are  seldom  used  in  iron  manufactories ;  the  application  of 
waste  heat  to  the  generation  of  steam  renders  steam-engines,  in  the 
opinion  of  all  experienced  manufacturers,  a  much  cheaper  element 
of  power.  But  the  purchase  of  steam-engines  requires  great  cau- 
tion ;  inattention  to  this  matter  has  resulted  in  great  loss  to  estab- 
lishments otherwise  well  arranged.  One  horse  power  is  consi- 
dered equal  to  33,000  pounds,  lifted  one  foot  high  in  one  minute. 
Many  other  equivalents  have  been  proposed  by  various  engineers ; 
but  this,  established  by  James  Watt,  is  generally  adopted.  Where 


MOTIVE   POWER.  461 

the  power  of  a  steam-engine  is  to  be  calculated,  the  services  of 
a  skillful  engineer  should  be  engaged ;  for  a  thorough  knowledge 
of  its  nature  is  indispensable.  But  there  is  an  elementary  rule  by 
which  we  may  calculate  the  power  approximately,  that  is,  by  the 
surface  of  a  steam  boiler  which  is  played  on  by  the  flame.  A 
well-constructed  steam-engine  requires  ten  square  feet  of  boiler  sur- 
face, acted  upon  by  the  fire,  to  produce  one  horse  power ;  this  ap- 
plies to  high  or  low  pressure  engines,  at  least  in  the  present  case. 
This  amount  of  power  cannot  be  produced  by  inferior  machines. 
Where  the  boilers  are  heated  by  the  waste  flame,  a  larger  surface  is 
required,  on  account  of  the  low  temperature  of  the  flame ;  that  is  to 
say,  at  the  blast  furnace  about  one-fourth  of  the  surface  of  the  boiler 
is  lost,  and  at  puddling  and  re-heating  furnaces,  rather  more  than 
ten  square  feet  must  be  taken.  The  application  of  this  rule  is, 
simply  to  measure  the  surface  of  that  part  of  the  boiler  which  is 
actually  exposed  to  the  flame.  If  a  cylindrical  boiler,  twenty  feet 
long,  and  three  feet  in  diameter,  with  no  flue  or  pipes,  is  more  than 
half  filled  with  water — the  brickwork  enclosing  just  half  of  the 
boiler — half  of  its  surface  will  be  exposed  to  the  action  of  the  flame; 
a  steam-engine  nourished  by  this  boiler  will  never  exert  a  power 
beyond  1.52x  3.14=7,  the  surface  of  one  whole,  or  two  half  heads, 

added  to  3xB^4x2°  =  94.2,  half  the  surface  of  the  cylinder, 
2 

which  gives  us  101.2  square  feet,  or  ten  horse  power.  By  this 
simple  method,  the  power  of  a  steam-engine  can  be  very  nearly 
ascertained,  that  is,  if  it  is  well-constructed,  for  this  calculation 
does  not  apply  to  an  ill-constructed  engine. 

In  locating  iron  works,  the  principal  object  which  the  manufac- 
turer should  seek  to  secure,  when  wood,  coal,  ore,  and  workmen 
can  be  advantageously  obtained,  is  facility  of  transportation.  The 
condition  of  roads,  canals,  navigable  rivers,  and  railroads  forms 
the  first  item  in  a  mercantile  balance  of  the  iron  business.  Though, 
compared  to  such  matters  as  these,  the  source  whence  power  is  ob- 
tainable is,  from  the  considerations  we  have  once  and  again  urged, 
one  of  small  importance ;  still,  as  the  careful  application  of  power 
constitutes  one  of  the  numerous  conditions  on  which  the  success  of 
iron  manufacture  depends,  it  deserves,  and  should  receive,  consi- 
derable attention.  At  some  of  the  Eastern,  and  most  of  the  West- 
ern works,  steam  is  generated  by  separate  fuel ;  but  at  most  of  the 
more  recently  erected  establishments,  it  is  generated  by  means  of 
waste  heat,  which  improvement  will  be  eventually  adopted  by  all 


462  MANUFACTURE   OF  IRON. 

the  iron  works.  It  is  true,  the  fuel  for  the  steam-engine  costs,  in 
many  cases,  almost  nothing ;  this  is  especially  the  case  at  those 
iron  works  situated  in  the  Western  coal  fields,  where  coal  can  be 
obtained  at  the  expense  of  digging  it,  that  is,  at  an  expense  of  from 
one  cent  to  one  and  a-quarter  cent  per  bushel ;  and  even  in  the 
city  of  Pittsburgh  itself,  where  slack  coal  can  be  bought  at  the 
same  price :  but  when  we  take  into  consideration  the  labor  which 
the  use  of  waste  heat  saves — such  as  that  of  the  fireman,  and  that 
which  is  required  to  carry  off  ashes — the  utility  of  its  application 
will  be  clearly  apparent. 

The  application  of  motive  power  is  a  subject  of  special  interest. 
The  idea  of  a  central  motion,  that  is  to  say,  of  a  power  which  ex- 
tends from  one  central  point  to  all  the  branches  of  an  establishment, 
receives  considerable  favor  from  engineers.  The  principle  may  be 
considered  a  true  one,  as  far  as  power  and  its  most  advantageous 
application  are  concerned ;  but  not  exactly  correct  in  relation  to 
iron  manufactories.  It  is  the  object  of  the  engineer  to  avoid  a 
waste  of  the  elements  of  power,  namely,  water  or  steam ;  but  with 
respect  to  steam,  economy  is  superfluous,  for,  in  the  iron  manufac- 
tory, more  than  sufficient  waste  heat  is  generated  to  produce  steam 
for  any  number  of  steam-engines,  and  to  counterbalance  any  loss 
of  power.  Waterwheels  should  not  be  erected  at  all,  where  lack  of 
water,  or  any  disturbance,  is  reasonably  to  be  expected.  In  iron 
works,  therefore,  the  only  consideration  which  should  influence  us 
as  to  the  motor  apparatus,  is  availability.  If,  with  respect  to  the 
manufacturing  operations,  two  engines  should  be  more  advantageous 
than  one,  that  number  should  undoubtedly  be  employed.  It  is  true, 
that  two  engines,  and  two  blast  machines,  occasion  a  greater  loss 
of  power  than  would  result  if  the  effect  of  both  was  united  in  one ; 
still,  if  any  advantage  arises  from  that  number,  loss  of  power  is 
not  a  valid  objection  to  their  use. 

At  blast  furnaces,  where  more  than  one  furnace  is  erected  at  the 
same  spot,  the  desire  to  concentrate  power,  and  to  generate  blast 
from  one  machine,  is  very  natural.  But  a  division  of  the  power  is 
more  practicable.  Every  experienced  iron  manufacturer  knows  that 
the  management  of  furnaces  cannot  be  conducted  according  to  arbi- 
trary regulations.  At  some  times  a  greater,  and  at  other  times  a 
less,  amount  of  blast  is  required,  under  conditions  apparently  the 
same.  In  a  well-conducted  manufactory,  the  keeper  or  founder  at 
each  furnace  should  be  enabled,  at  all  times,  to  increase  or  modify 
the  power  of  the  blast.  Nothing  can  ensure  this  result,  if  the  blast 


MOTIVE   POWER.  463 

is  drawn  from  a  common  source.  In  most  cases,  separate  engines 
are  erected  for  each  furnace.  Due  attention  to  this  subject,  on  the 
part  of  the  iron  manufacturer,  will  undoubtedly  result  in  the  con- 
viction that,  in  this  case,  a  division  is  more  advantageous  than  a 
concentration  of  power. 

A  division  of  power  is  still  more  essential  in  a  rolling  mill  than 
at  blast  furnaces;  and  a  separation  of  mill  and  forge  power  is  gene- 
rally made.  If  we  reflect  upon  the  waste  of  iron,  in  re-heating 
and  puddling  furnaces,  which  is  occasioned  by  delay,  it  is  evident 
that  the  utmost  dispatch  is  required  in  the  discharge  of  their  con- 
tents. A  concentrated  power  must  be  strong  indeed  if  it  does 
not  fail  when  all  the  machinery  of  a  rolling  mill  is  set  in  motion. 
Even  though  the  engine  is  capable  of  impelling  this  machinery,  slow 
motion  is  but  too  apt  to  be  the  consequence.  The  argument  that  a 
steam-engine  or  waterwheel  may  be  made  sufficiently  strong  to 
move  the  machinery  of  a  mill,  though  a  power  of  100  or  1000  horses 
is  required,  does  not  apply  against  our  objections  to  a  concentrated 
power.  Different  trains  of  rollers  require  different  speed.  This 
variation  of  speed  can  be  effected  by  cog-wheels,  or  by  means  of 
leather  belts,  as  practiced  in  some  establishments ;  but  the  same 
train  requires  different  speed  at  different  times.  This  object  cannot 
be  realized  where  a  single  engine  impels  the  whole  machinery  of  an 
establishment.  Another  advantage  which  attends  the  division  of 
power  is,  that  an  occasional  disturbance  in  one  train,  a  circum- 
stance which  frequently  occurs,  does  not  affect  the  machinery  of 
another  train.  The  most  advantageous  division  is  that  in  which 
each  train  is  impelled  by  a  separate  power,  which  can  be  regulated 
by  the  foreman  with  comparative  ease.  The  squeezer  ought  to  be 
moved  by  an  independent  power. 

Various  attempts  have  been  made  to  connect  diverse  tilthammers 
with  one  central  power.  This  appeared  to  be  practicable,  particu- 
larly with  regard  to  small  hammers  which  make  300  or  400  strokes 
per  minute.  Nevertheless,  all  such  experiments  have  failed,  and 
at  present  each  tilthammer  requires  its  own  waterwheel,  or  its 
own  steam-engine.  A  fair  opportunity  to  construct  a  steam  ham- 
mer, of  100  or  200  pounds  weight,  making  400  strokes  per  minute, 
which  shall  be  simple  and  independent,  is  thus  afforded  to  a  skillful 
and  enlightened  engineer. 


464  MANUFACTURE   OF   STEEL. 


CHAPTER   XI. 

MANUFACTURE  OF  STEEL. 

THOUGH  this  subject  is  not  comprised  within  the  range  of  our  im- 
mediate investigations,  and  therefore  cannot  be  said  to  form  an  inte- 
gral portion  of  this  work,  still,  as  it  is  one  of  great  national  interest, 
and  as  the  successful  manufacture  of  steel  depends  chiefly  on  the 
elements  from  which  it  is  made,  namely,  iron  ore  and  coal,  we  shall 
devote  a  few  pages  to  its  consideration.  We  regret  that  we  cannot 
devote  to  it  a  degree  of  attention  commensurate  with  its  import- 
ance. The  United  States  are  at  present,  and  will  be,  for  some  time 
to  come,  dependent  upon  other  countries  for  steel.  Still,  iron  ore 
exists,  within  our  widely-extended  boundaries,  which  is  adapted  to 
make  an  article  of  the  best  quality.  The  quality  of  steel  depends 
both  on  ore  and  on  manipulation;  but  the  advantages  derivable  from 
the  union  of  these  elements  are  realized  with  much  greater  difficulty 
than  would  at  first  sight  appear.  Steel  is  composed  chiefly  of  iron 
and  carbon ;  yet  these  will  produce  only  a  poor  and  brittle  article. 
Good  steel  contains  a  variety  of  elements,  almost  all  of  those,  in 
fact,  which  we  consider  impurities  of  iron  when  present  in  excess. 
We  shall  not  dwell  upon  the  attempts  formerly  made  in  the  United 
States  to  manufacture  steel.  Recently,  a  new  enterprise,  under  the 
name  of  the  Adirondac  Iron  and  Steel  Manufacturing^Company, 
has  been  started,  which  promises  to  be  successful.  This  establish- 
ment is  so  located  as  to  enjoy  better  facilities  than  any  similar  estab- 
lishment in  this  country  has  ever  possessed.  To  what  extent  this 
company,  whose  blast  furnaces  are  in  Essex  county,  N.  Y.,  and 
whose  steel  works  are  in  Jersey  City,  will  realize  the  expectations 
of  the  public,  it  remains  to  be  seen.  In  Pittsburgh,  attempts  have 
been  made  to  manufacture  steel.  But  we  doubt  whether  an  article 
of  good  quality  can  ever  be  produced  in  that  region.  Fuel  is  favor- 
able in  the  west ;  but  this  is  not  the  case  with  ore,  at  least  not  in 
those  sections  of  country  which  lie  between  the  Mississippi  River 
and  the  Alleghany  Mountains.  Of  what  quality  the  ore  will  prove 


MANUFACTURE   OF   STEEL.  465 

to  be  beyond  the  Mississippi,  we  have  no  definite  means  of  know- 
ing ;  but  appearances  indicate  a  more  encouraging  prospect  than  is 
afforded  by  the  secondary  strata,  and  the  coal  regions.  As  no 
steel  manufactory  of  established  renown  exists  in  our  country,  we 
shall  proceed  to  the  examination  of  the  subject  before  us: — 

a.  Steel  is  divided  into  four  distinct  classes  :  Damascus  steel ; 
German  steel ;  Blistered,  or  blister  steel,  to  which  class  shear  steel 
belongs;  and  Cast  steel.  The  first  is  made  directly  from  the  ore, 
or  by  welding  steel  rods  and  iron  rods  together ;  the  second  from 
pig  metal,  by  depriving  the  latter  of  a  portion  of  its  carbon  and 
impurities;  the  third  from  bar  iron,  by  impregnating  it  with  car- 
bon ;  and  the  fourth  class,  or  cast  steel,  may  be  made  from  either  of 
the  others,  by  melting  the  steel  in  a  crucible ;  still,  blistered  steel 
appears  to  be  the  most  advantageous,  so  far  as  quality  is  concerned. 

I.  Damascus  Steel. 

This  steel  derives  its  name  from  Damascus,  a  city  in  Asia.  The 
swords  or  scimitars  of  Damascus  present  upon  their  surface  a 
watery  appearance,  a  variegation  of  streaks,  of  a  silvery  white, 
black,  and  gray  color,  and  fine  and  coarse  lines,  exhibiting  regular 
and  irregular  figures.  The  excellent  quality  of  these  blades  is  pro- 
verbial; they  unite  hardness  to  great  elasticity.  Genuine  Damascus 
steel  is  made  directly  from  iron  ore  ;  and  meagre  as  our  knowledge 
is  concerning  the  subsequent  manipulations,  such  as  forging  and 
hardening,  we  know  that  the  steel  is  smelted,  in  a  kind  of  Catalan 
forge,  from  red  oxide  of  iron,  a  red  clay  ore  found  in  transition  slate. 
It  is  generally  believed  that  the  great  strength  of  this  steel  is  to  be 
attributed  to  a  small  quantity  of  aluminum  which  enters  into  its 
composition,  and  which  is  derived  from  the  clay  of  the  ore — an 
opinion  which  has  this  fact  in  its  favor,  that  no  material  imparts  a 
greater  degree  of  tenacity  to  iron  than  alumina.  Great  exertions 
have  been  made  to  imitate  this  steel,  in  which,  of  all  nations,  the 
French  have  been  the  most  successful.  They  have  succeeded  in 
imitating  not  only  irregular  figures,  but  arabesques  and  initials,  in 
the  most  beautiful  manner ;  still,  the  French  is  far  less  tenacious 
and  hard  than  the  genuine  Damascus  steel.  The  virtue  of  the 
latter,  therefore,  must  be  sought  for  in  the  ore  from  which  it  is  made. 
We  are  not  aware  that  the  United  States  afford  any  clay  ore  of 
good  quality.  True,  there  is  an  abundance  of  this  ore  in  the  State 
of  Arkansas ;  but  whether  it  will  ever  be  of  service  in  the  manu- 
facture of  steel  is  more  than  we  are  able  to  say.  The  whole  subject 
30 


466  MANUFACTURE   OF  STEEL. 

is  one  of  but  little  national  interest ;  for  the  application  of  this  kind 
of  steel  is  very  limited. 

II.   Grerman  Steel. 

This  steel  is  made  in  two  different  ways :  either  directly  from 
the  ore,  or  by  converting  the  ore  into  pig  metal,  and  then  into 
steel.  The  steel  manufactured  by  the  first  method  is  generally 
crude  and  irregular,  and  therefore  this  method  is  seldom  practiced. 

a.  The  stuck-oven,  or  wulf  s-oven,  described  in  Chapter  III.,  as 
well  as  the  Catalan  forge,  is  one  of  the  furnaces  employed  in  the 
manufacture  of  steel  from  ore.     In  making  steel,  the  blast  is  di- 
rected more  upon  the  fuel  than  upon  the  iron.     The  tuyere  is  level. 
The  iron  is  impregnated  with  carbon.     The  reverse  is  the  case  in 
the  manufacture  of  iron.     In  the  blue  oven,  a  kind  of  pig  metal  is 
frequently  made,  which  is  almost  pure  steel,  but  it  is  coarse,  and 
never,  even  after  the  best  refining,  makes  a  good  article.     All 
manipulations,  the  object  of  which  is  to  make  steel  directly  from 
the  ore,  are,  as  we  have  stated,  unprofitable. 

b.  To  this  class  belongs  the  manufacture  of  woots,  or  East  In- 
dian steel.     This  is  certainly  a  good  steel ;  but  it  cannot  be  imi- 
tated in  this  country,  in  consequence  of  the  high  price  of  labor. 
Woots  is  smelted  directly  from  the  ore,  the  black  magnetic  oxide 
of  iron,  in  furnaces  five  or  six  feet  high,  of  the  form  of  our  foundry 
cupolas.     Previously  to  smelting,  the  ore  is  finely  pounded  and 
washed,  to  remove  impurities — a  manipulation  too  expensive  for 
imitation  in  the  United  States. 

c.  The  manufacture  of  steel  from  pig  metal  does  not  depend  so 
much  upon  the  manipulations  in  the  forge,  as  upon  the  quality  of 
the  metal.     The  ores  generally  employed  are  the  crystalized  car- 
bonate, spathic  ore,  often  mixed,  in  a  slight  degree,  with  hematite, 
and  the  rich  red  peroxides.     Magnetic  ores  do  not  answer  for  such 
work,  and  are  therefore  but  seldom  used.     The  same  may  be  said 
in  relation  to  the  hydrated  oxides.  Pig  metal  for  steel  manufacture 
is  smelted  with  as  little  lime  or  other  flux  as  possible.     The  prin- 
cipal flux  on  which  we  rely  is  manganese,  but  this  always  exists  in 
the  ore,  and  is  never  used  as  an  artificial  admixture,  though  it  is 
possible  that  an  artificial  flux  might  be  made  of  it.    Steel  metal  is, 
in  most  cases,  white.     It  is  smelted  by  rather  more  ore  than  that 
which  will  make  gray  iron;  but  not  with  so  heavy  a  burden  as  that 
which  will  make  white  iron  containing  carbon  in  small  amount. 
Any  ore  which  contains  foreign  matter  in  such  large  amount  as  to 


MANUFACTURE   OF  STEEL.  467 

make  the  addition  of  lime  as  a  flux  necessary,  does  not  make  good 
steel  metal.  The  only  mode  of  working  the  furnace  is,  of  course, 
by  means  of  charcoal  and  cold  blast. 

The  forge  fires,  employed  in  converting  the  metal  into  steel,  do 
not  differ  materially  from  those  in  which  iron  is  made.  The  hearth 
of  the  former  is  generally  larger  and  deeper,  and  the  blast  is  strong- 
er than  that  of  the  latter.  But  little  iron  is  connected  with  it.  The 
bottom  is  generally  formed  of  sandstone,  and  the  sides  of  braise, 
or  charcoal  dust  mixed  with  clay.  We  think  that  good  fire  brick 
will  prove  superior  to  any  other  material.  The  practical  manipula- 
tion at  these  forge  fires  varies  according  to  locality,  to  the  form  of 
the  furnace,  and  to  the  character  of  the  workmen.  The  main  prin- 
ciple involved  may  be  generalized  under  the  following  proposition : 
If  it  is  our  design  to  make  steel,  instead  of  iron,  we  should  melt 
the  metal  before,  and  off  from  the  tuyere;  and  we  should  keep  the 
melted  metal  always  below  the  blast,  and  never  bring  it  above,  or 
into  the  blast.  By  due  attention  to  locality,  everything  else  may 
be  easily  regulated.  A  skillful  workman  will  soon  ascertain  that  a 
flat  hearth,  an  iron  lining,  and  a  strongly  dipped  tuyere  will  not 
make  steel,  though  it  will  make  iron;  and  that  a  weak  blast  will  tend 
to  produce  iron.  In  this  country,  there  is  no  prospect  of  making 
steel  directly  from  the  crude  metal,  unless  ores  of  a  very  different 
character  from  those  we  at  present  possess  shall  be  discovered.  Such 
steel  requires  those  rich  ores  which  contain  manganese;  and  these, 
to  all  appearances,  do  not  exist  on  this  side  of  the  Mississippi.  It 
is  possible  that  a  kind  of  white  pig  metal,  suitable  for  the  manu- 
facture of  German  steel,  might  be  smelted  from  magnetic  ore ;  but 
of  this  there  is,  at  present,  no  prospect.  Surely,  this  cannot  be 
effected  by  hot  blast,  and  so  long  as  our  furnace  owners  use  such 
blast  in  the  manufacture  of  steel  metal,  they  will  not  succeed  in 
producing  a  good  article. 

Were  it  even  possible  to  manufacture  such  pig  metal,  it  is  doubt- 
ful whether  it  would  prove  an  available  article ;  for,  when  we  con- 
sider the  amount  of  labor  and  fuel  it  requires,  it  is  evident  that  the 
cost  of  the  steel  would  render  the  experiment  a  somewhat  hazardous 
one.  In  making  steel  from  good  metal,  the  loss  of  iron  amounts  to 
from  twenty  to  thirty  per  cent. ;  and  about  a  ton,  or  a  ton  and  a 
quarter  are  produced  per  week.  Very  nearly  600  bushels  of  char- 
coal are  consumed  per  ton.  Where  ore  and  coal  are  favorable,  two 
tons  per  week  may  be  made,  with  a  proportionate  saving  of  fuel. 
Still,  seldom  less  than  300  bushels  per  ton  are  consumed,  and  the 
waste  of  iron  is  seldom  less  than  twenty  per  cent. 


468  MANUFACTURE   OF   STEEL. 

The  crude  steel,  the  result  of  the  first  operation,  is  generally 
thrown,  when  red  hot,  into  cold  water,  then  broken  and  sorted.  The 
most  silvery  part,  of  the  finest  grain,  is  No.  1.  Fibrous,  or  par- 
tially fibrous  bars  are  reserved  for  iron.  They  make  a  superior 
quality  of  bar  iron.  Bluish-looking  steel  is  also  thrown  aside,  for  it 
will  become  fibrous  iron  before  its  impurities  can  be  removed.  The 
crude  steel,  drawn  out  into  bars  an  inch  or  an  inch  and  a  quarter 
square,  is  placed  in  piles  composed  of  six  or  eight  pieces,  then 
welded,  and  drawn  out  into  smaller  bars.  This  process,  called  re- 
fining, is  repeated  three  or  four  times,  and  each  time  the  number  of 
bars  in  the  pile  is  increased.  The  smaller  the  bars  of  steel,  and 
the  greater  the  number  of  them  placed  together,  the  more  perfect 
will  be  the  refined  steel.  The  piles  are  heated  in  a  large  black- 
smith's fire,  by  stone  coal,  which  must  be  sufficiently  bituminous  to 
form  an  arch  over  the  fire.  Coal  slack,  mixed  with  loam,  is  fre- 
quently used  for  this  purpose;  but  it  increases  the  waste  of  steel. 
The  hammer  used  for  drawing  steel  should  be  light,  weighing  no 
more  than  150  pounds,  and  ought  to  make  from  300  to  400  strokes 
per  minute.  Great  skill  and  dexterity  are  required  to  draw  steel 
bars.  It  is  highly  important  to  perform  this  operation  well,  as  the 
quality  of  the  steel  is,  in  some  measure,  dependent  upon  the  man- 
ner in  which  it  has  been  hammered. 

d.  In  those  countries  where  German  steel  is  made,  a  remarkable 
article  is  manufactured,  which  deserves  our  notice.  It  is  harder 
than  the  best  cast  steel,  but  so  brittle  that  it  cannot  bear  any  bend- 
ing when  cold.  This  article  is  cast  iron.  It  is  derived  from  the 
re-melted  steel  metal.  From  200  to  250  pounds  of  this  metal  are 
generally  melted  in.  When  that  quantity  is  melted  down  in  the 
bottom  of  the  forge  hearth,  a  small  portion  of  it  is  let  off;  it  should 
be  tapped  as  low  at  the  bottom  as  possible.  This  mass,  which  flows 
like  cast  iron  or  cast  steel,  is  broken  into  small  pieces,  and  pounded 
into  a  flat  piece  of  wrought  iron,  which  has  a  brim  drawn  up  around 
it.  This  piece  serves  as  a  crucible.  It  is  covered  with  loam,  and 
exposed  to  a  heat  which  will  melt  the  cast  iron,  and  unite  it  firmly 
with  the  wrought  iron.  The  former  then  forms  a  thin  coating  of 
steel,  over  the  one  side  of  the  iron,  of  immense  hardness.  This 
does  not  become  soft,  even  though  a  long  time  is  consumed  in  tem- 
.pering  it.  Wrought  iron  plates,  furnished  with  such  a  coating  of 
steel,  are  used  as  drawplates  for  wire.  The  holes  for  the  wire  are 
punched  when  it  is  warm,  for,  when  cold,  its  hardness  is  so  ex- 
treme, that  no  drill  bit  can  make  any  impression  on  it. 


MANUFACTURE   OF   STEEL.  469 

III.  Iron  for  .Blistered  Steel 

The  manufacture  of  German  steel  in  this  country  is  not  very 
likely  to  be  successful;  in  fact,  no  attempt  to  make  it  is  likely  to 
be  accompanied  with  any  useful  result.  The  manufacture  of  blis- 
tered and  cast  steel  is  more  appropriate  to  our  wants  and  habits. 
This  branch  of  industry  is  highly  cultivated  in  England,  and  to  that 
country  must  we  look  for  the  requisite  information  concerning  it. 
It  is  generally  known  that  England  does  not  produce  any  iron  suit- 
able for  the  manufacture  of  steel,  and  that  she  purchases  all  that 
she  needs  for  this  purpose  from  Sweden  or  Russia.  Therefore,  we 
must  depend  upon  Russia  and  Sweden  for  the  knowledge  of  the 
mode  of  working  it,  and  the  kind  of  materials  from  which  iron  for 
the  steel  factories  is  made. 

The  peculiarities  of  such  iron  are  so  remarkable,  that,  by  means 
of  the  most  accurate  chemical  analysis,  we  cannot  detect  any 
difference  between  a  given  kind  which  produces  a  superior,  and 
another  kind  which  produces  an  inferior,  steel.  Were  it  possible 
to  detect  this  difference,  it  would  prove  to  exist  in  the  cinders. 
Investigations  of  this  nature  would  lead  us  beyond  our  limits ;  and 
as  the  facts  available  can  be  found  only  by  experience,  it  may  an- 
swer quite  as  well  to  abandon  scientific  inquiries  at  present.  The 
iron  from  which  blistered  steel  is  made  is  a  soft,  fibrous,  often 
grained  wrought  iron,  and  of  a  peculiar,  silvery  whiteness.  It  is 
made  from  mottled  pig  iron,  smelted  from  magnetic  ore  by  char- 
coal and  cold  blast. 

a.  In  the  State  of  New  York,  we  have  an  abundance  of  magnetic 
ore  of  sufficiently  good  quality  to  make  an  excellent  steel,  if  its  na- 
ture and  the  mode  of  working  it  were  once  thoroughly  understood. 
Magnetic  ore  exists  in  New  Jersey;  but,  so  far  as  we  can  judge,  it 
is  not  sufficiently  pure  for  the  manufacture  of  good  steel.  Whether 
the  Missouri  ore  will  ever  prove  useful,  remains  to  be  tried.  Though 
we  believe  its  quality  to  be  good,  we  cannot  speak  of  it  with  the 
same  confidence  that  we  can  speak  in  relation  to  that  of  the  New 
York  ore.  No  ores  of  the  coal  formation — the  hydrates,  and  red 
clay  ores  of  Pennsylvania,  Ohio,  Tennessee,  and  Alabama — pre- 
sent any  claims  worthy  of  our  attention.  Should  these  ores  make 
steel,  they  could  not  be  employed  except  at  great  expense,  while 
the  article  produced  would  be  of  very  poor  quality. 

In  making  pig  iron  for  the  manufacture  of  steel,  the  ore  should 
be  carefully  roasted  by  wood,  charcoal,  or  braise.  The  height  of 


470  MANUFACTURE   OF  STEEL. 

the  blast  furnace  must  not  exceed  thirty-five  feet,  and  the  result  is 
still  more  favorable  when  it  does  not  exceed  thirty  feet.  The  boshes 
should  measure  about  nine  or  nine  and  a  half  feet.  There  ought  to 
be  either  no  hearth  at  all,  as  in  the  Swedish  or  Styrian  furnaces, 
described  in  Chapter  III.,  or  one  that  is  very  low.  Blast  of  medium 
strength,  and  tuyeres  somewhat  inclined  into  the  hearth,  are  requi- 
site. Hot  blast  must  be  rejected  altogether.  In  fact,  the  operation 
should  be  conducted  in  such  a  manner  as  to  produce  mottled  iron 
of  great  purity.  This  will  be  understood  by  reference  to  Chapter 
III.  In  fluxing  the  ore,  lime  can  be  employed,  but  in  such  limited 
quantity  as  not  to  cause  the  furnace  to  smelt  gray  or  white  iron, 
for  neither  will  be  serviceable  for  the  manufacture  of  good  steel. 

b.  In  converting  pig  into  bar  iron,  the  German  forge,  described 
in  Chapter  IV.,  is  generally  employed  in  Sweden,  and  for  this  pur- 
pose may  be  considered  more  perfect  than  any  other.  The  refining 
process  resembles  the  boiling  of  iron.  This  is  required  to  make  the 
texture  of  the  iron  as  uniform  as  possible.  White  pig  metal  will 
not  boil,  and  it  works  too  fast.  Gray  pig  metal  contains  a  large 
amount  of  impurities,  and  the  greatest  attention  at  the  forge  will  not 
remove  them  in  sufficient  amount  to  answer  any  practical  purpose. 
We  have  serious  doubts  whether  puddled  iron  is  adapted  for  making 
steel,  at  least  steel  of  good  quality;  and  we  should  hesitate  to  re- 
commend its  use.  We  shall  give  a  description  of  what  should  be 
the  negative  and  positive  qualities  of  iron ;  and  then,  by  reference 
to  Chapter  IV.,  the  principles  and  manipulations  necessary  to  be 
observed  in  its  manufacture  may  be  understood. 

In  making  blistered  steel,  it  is  essential  to  consider  not  only  the 
quality,  that  is,  the  chemical  composition,  of  the  iron,  but  also  its 
form.  The  bars  are  generally  flat;  good  qualities  are  from  an  inch 
and  a  quarter  to  two  inches  in  width,  and  half  an  inch  thick.  For 
ordinary  steel,  and  for  cast  steel,  the  thickness  of  the  bars  may  be 
three-quarters  of  an  inch ;  but  in  these  cases,  more  time  is  not 
only  required  in  blistering,  but  the  heart  of  the  bar  is  still  imper- 
fectly carbonized.  Thin  bars  work  faster,  and  make  a  more  uni- 
form steel,  than  thick  and  heavy  bars.  The  latter  are  always  more 
or  less  raw  inside,  and  contain  too  much  carbon  outside.  If  the  iron 
is  very  pure,  it  may  be  short,  that  is,  without  fibres.  It  may  be 
hard,  if  it  is  at  the  same  time  strong.  Impure  iron  will  not  make 
steel  of  good  quality.  As  iron  void  of  fibres  is  generally  more  im- 
pure than  that  containing  fibres,  the  safest  plan  we  can  adopt  is  to 
convert  all  the  iron  into  fibrous  iron.  Coarse,  fibrous  iron,  what- 


MANUFACTURE   OF   STEEL. 


471 


ever  may  be  its  strength,  does  not  make  good  steel.  That  with  black 
spots  or  streaks  of  cinder  must  be  avoided  by  all  means.  The  in- 
dications of  a  good  iron  are  a  silvery  white  color,  short  fine  fibres,  a 
bright  metallic  lustre,  and  an  aggregation  so  uniform  that  black 
spots  cannot  be  detected  with  a  lens.  The  transformation  of  bar 
iron  into  steel  requires  no  special  skill  or  knowledge.  The  quality  of 
the  steel  is  determined  by  the  quality  of  the  iron  from  which  it  is 
manufactured. 

IV.  Blistered  Steel 
Fig.  148  exhibits  a  section  of  a  furnace  for  converting  wrought 

Fig.  148. 


Furnace  for  making  blistered  steel. 

iron  into  blistered  steel.  The  furnace,  externally,  is  twelve  or 
fifteen  feet  wide,  and  twenty  or  twenty-five  feet  deep.  The  conical 
chimney,  forty  or  fifty  feet  high,  is  designed  to  lead  the  smoke  above 
the  roof  of  the  factory,  a,  a  Two  boxes,  made  of  sandstone  tiles, 
two  or  three  inches  thick.  For  this  purpose,  the  fine-grained, 


472  MANUFACTURE   OF   STEEL. 

white  sandstone,  called  kaolin,  is  a  superior  article.  In  the  Western 
coal  fields,  fine  deposits  of  slaty  sandstone  are  found.  These  slabs 
are  bedded  upon  fire  brick,  for  the  fire-flue  is  not  one  continuous 
opening,  but  a  series  of  flues,  -which  are  designed  to  keep  the  slabs 
in  their  position,  and  the  joints  covered.  The  boxes  are  not  less 
than  twenty-four,  or  more  than  thirty-six  inches  square,  and  from 
ten  to  sixteen  feet  in  length,  which  may,  perhaps,  of  all  sizes,  be 
considered  the  most  favorable.  In  England,  these  boxes  are  gene- 
rally made  of  fire  brick — that  is,  of  fire  tiles  made  of  the  proper 
size — which  is  preferable  to  stones,  though  more  expensive.  The 
boxes  are  enclosed  in  a  large  furnace,  as  shown  in  the  drawing, 
with  grate,  and  fire  brick  arch.  5,  b  Two  square  holes,  at  one 
end  of  the  furnace ;  these  serve  for  the  admission  of  the  iron,  and 
for  the  entrance  and  exit  of  the  workmen.  The  small  holes  ex- 
hibited at  one  end  of  the  boxes  are  proof  holes,  through  which  one 
or  more  of  the  iron  bars  may  be  passed,  for  the  purpose  of  testing 
the  degree  of  cementation,  and  the  progress  of  the  work.  In  the 
chests  or  boxes  a  a,  the  iron  is  imbedded  and  carefully  laid  in  the 
cement  edgewise.  The  cement  is  composed  of  one  part  of  hard 
charcoal,  one-tenth  part  of  wood  ashes,  and  one-twentieth  part  of 
common  salt.  The  mixture  is  ground  into  a  coarse  powder  under 
edge-wheels.  If  the  box  is  ten  feet  in  length,  the  iron  bars  may 
be  nine  feet  and  ten  inches.  The  cement  is  laid  about  two  inches 
deep  in  the  bottom  of  the  box.  The  bars  of  iron  are  then  put  edge- 
wise, separated  by  three-fourths  of  an  inch  space.  This  space  is 
filled  with  cement,  and  the  top  of  the  bars  covered  to  the  depth  of 
half  an  inch.  Upon  this,  another  layer  of  bars  is  set,  but  in  such 
a  manner  that  the  second  layer  occupies  the  space  which  separates 
the  bars  of  the  first  layer.  We  proceed  in  this  manner  until  the 
box  is  filled  to  within  six  inches  of  its  top.  The  remaining  space 
is  filled  with  old  cement  powder,  on  the  top  of  which,  finally,  damp 
sand  or  fire  tiles  are  placed.  The  fire  ought  to  proceed  slowly,  so 
that  three  or  four  days  shall  elapse  before  the  furnace  and  the  cement 
boxes  assume  a  cherry-red  heat.  In  fact,  the  fire  should  be  con- 
ducted in  such  a  manner  that  the  heat  may  be  slightly  increased 
every  day  during  the  whole  course  of  the  operation.  A  diminution 
of  the  heat,  from  the  time  of  starting,  occasions  a  loss  of  fuel  and 
time,  and  is  injurious  to  the  chests.  A  well-conducted  heat  will 
finish  a  small  box  in  four  or  five  days,  and  a  couple  of  boxes  three 
feet  square  in  ten  or  twelve  days.  The  furnace  and  boxes  should 
be  cooled  very  slowly,  for  a  sudden  change  of  temperature  is  very 


MANUFACTURE   OF  STEEL.  473 

apt  to  break  the  fire  tiles,  or  sandstone  slabs,  of  which  the  boxes 
are  constructed.  The  trial-bar,  which  passes  through  the  small 
hole  in  one  of  the  ends  of  the  box,  and  in  a  corresponding  hole  in 
the  furnace  wall,  is  somewhat  longer  than  the  other  bars,  so  as  to 
be  taken  by  a  pair  of  tongs,  and  pulled  out  of  the  box.  There  are 
frequently  several  of  such  bars,  for  a  bar  that  is  once  pulled  cannot 
be  returned  ;  and  if,  in  a  case  in  which  there  is  but  one  trial-bar  in 
the  chest,  the  bar  is  pulled  too  soon,  no  further  opportunity  of  test- 
ing the  progress  of  cementation  is  afforded.  The  trial-bars  are  not 
sufficiently  long  to  project  over  the  wall  of  the  chest.  The  trial- 
hole  is  closed  by  a  clay  stopper.  Six  days  may  be  considered  a 
sufficient  time  for  blistering  bars  of  common  steel,  such  as  spring 
steel,  saw  blades,  and  common  files ;  eight  days  for  shear  steel,  and 
steel  for  common  cutlery;  and  ten  or  eleven  days  for  the  better 
qualities  of  steel,  and  common  cast  steel.  Rods  for  the  finer  sorts 
of  blistered,  and  the  finest  kinds  of  cast  steel,  are  returned  to  the 
boxes  after  the  first  heat,  and  receive  two  or  three  blistering  heats, 
according  to  the  quality  of  steel  we  wish  to  obtain.  From  eight  to 
twelve  tons  of  iron  may  be  charged  in  two  chests,  and  from  four  to 
eight  tons  in  case  the  furnace  contains  but  one  chest.  Two  small 
chests  are  preferable  to  one  large  chest.  The  smaller  the  chest,  the 
more  uniform  will  the  steel  become.  The  regulation  of  the  fire  in 
the  furnace  is  a  somewhat  delicate  operation.  Iron  of  different 
qualities  requires  a  different  degree  of  heat.  The  heat,  however, 
may  be  easily  managed,  if  we  recollect  that  it  should  steadily  in- 
crease every  day.  If  it  is  not  sufficiently  strong,  the  iron  will 
absorb  but  very  little  carbon,  and  the  work  will  proceed  slowly. 
If  the  heat  is  too  great,  the  rod  iron  will  be  converted  into  cast  iron, 
or,  at  least,  into  something  similar  to  it;  for,  after  being  once  over- 
heated, it  will  not,  even  with  the  greatest  labor  and  attention,  make 
good  steel.  If  the  heat  is  carried  so  far  as  to  melt  the  blistered 
iron  in  the  boxes,  it  is  converted  into  white  plate  metal — the  kind 
from  which  German  steel  is  manufactured.  But  this  melting  can- 
not well  take  place,  and  if  it  should  occur,  the  slow  cooling  of  the 
chests,  which  is  equivalent  to  tempering,  will  transform  the  white 
metal  into  gray  cast  iron.  The  latter  is  converted  into  steel  with 
greater  difficulty  than  the  white  metal. 

Blistered  steel,  taken  from  the  chest,  is  very  brittle;  the  excel- 
lence of  its  quality  is  in  proportion  to  its  brittleness.  The  presence 
of  fibres  indicates  that  the  cementation  is  unfinished.  A  fine-grained  ? 
white  aggregation,  like  iron  rendered  cold-short  by  phosphorus,  in- 


474  MANUFACTURE   OF   STEEL. 

dicates  that  the  cementation  has  not  advanced  beyond  its  first  stages; 
A  crystaline  form  of  the  grains  is  an  indication  of  imperfect  cement- 
ation, or  of  too  low  a  heat,  or  bad  iron;  still,  the  best  kind  of  iron 
will  exhibit  these  crystals:  and  they  can  be  observed  by  the  lens, 
if  the  temperature  of  the  chests  has  not  been  kept  sufficiently  high. 
If  we  desire  a  good  article,  a  repetition  of  the  operation  is,  in  such 
cases,  necessary.  The  grains  of  good  steel  appear  like  round 
globules,  when  taken  from  the  chest  and  broken.  After  an  imper- 
fect cementation,  the  color  of  the  steel  is  white.  Good  blistered 
steel  should  be  of  a  grayish  color  and  of  a  bright  lustre ;  and  it 
should  exhibit  a  coarse  grain,  as  though  it  were  an  aggregation  of 
mica,  or  leaves  of  plumbago.  That  which  exhibits  a  fine  grain,  of 
crystaline  form,  and  which  is  of  a  white  color,  is  always  a  poor 
article.  But  one  degree  of  heat  is  favorable  for  each  kind  of  iron. 
If  we  hit  upon  that  exact  degree,  the  operation  goes  on  well.  If 
otherwise,  we  cannot  expect  a  favorable  result.  The  composition 
of  the  cement  and  the  construction  of  the  boxes  and  furnace  have 
but  little  influence  upon  the  quality  of  the  steel.  Where  the  iron  is 
of  the  best  quality,  and  where  the  degree  of  heat  is  most  favorable, 
the  fracture  of  a  bar  taken  from  the  chest  will  exhibit  the  largest 
grains  or  leaves.  An  indication  of  good  iron  is  its  increase  of 
weight  in  cementation.  While  bad  iron  neither  gains  nor  loses  in 
weight,  iron  of  good  quality  will  gain  at  the  rate  of  from  fifteen  to 
twenty  per  cent.  This  applies  especially  to  strong  and  pure  iron. 
The  surface  of  the  rods,  whatever  number  of  blisters  it  may  have 
when  taken  from  the  chest,  must  be  clean.  Bad  iron  makes  but  few 
blisters,  or  none  at  all ;  the  surface  of  the  rods  is  rough.  With  the 
quality  of  the  iron  the  number  and  size  of  the  blisters  increase. 
Danemora  iron  draws  blister  close  to  blister,  and  almost  all  of  equal 
size.  Common  iron,  that  is,  charcoal  iron,  raises  but  few  blisters, 
and  these  are  of  irregular  size.  The  best  qualities  of  puddled  iron 
raise  but  few  blisters. 

a.  As  might  be  expected,  the  texture  and  quality  of  one  bar,  as 
well  as  the  average  which  a  chest  contains,  cannot  be  uniform. 
The  interior  of  a  bar,  like  the  interior  of  the  box,  will  be  imperfect, 
while  the  external  parts  will  be  overdone.  The  steel  should,  there- 
fore, be  broken,  assorted,  and  refined.  Pieces  of  a  uniform  grain, 
as  well  as  those  including  the  extremes  of  quality,  are  piled,  welded, 
and  drawn  out  into  bars.  This  process  must  be  repeated,  if  the  grain 
is  not  sufficiently  uniform  for  the  desired  purpose.  Upon  the  skill 
of  the  hammerman  the  quality  of  the  steel,  in  a  considerable  de- 


MANUFACTURE   OF   STEEL.  475 

gree,  depends.  Slow  and  heavy  strokes  and  high  heats  depreciate 
its  value,  while  its  quality  is  improved  by  a  low  heat  and  fast  work. 
Rolling  steel  in  a  rolling  mill,  or  welding  it  in  a  re-heating  furnace, 
makes  it  brittle,  and  transforms  it  into  a  kind  of  cast  iron.  This 
result,  however,  can  be  partially  remedied  by  again  bringing  the 
steel  to  the  hammer. 

b.  The  influence  of  the  tilthammer  upon  the  iron  is  nowhere  more 
observable  than  in  the  manufacture  of  steel.  It  is  impossible  to 
make  good  steel  independently  of  proper  hammer  machinery.  The 
temperature  at  which  the  hammering  should  be  performed  is  a  mat- 
ter of  considerable  importance.  The  steel  will  be  spoiled  equally 
by  a  too  high,  and  by  a  too  low  heat.  The  secret  of  success  ap- 
pears to  be  the  prevention  of  crystalization,  which  takes  place  at 
certain  temperatures  of  the  metal.  Under  favorable  conditions, 
definite  compounds  of  carbon  and  iron  are  formed ;  and  these  com- 
pounds crystalize.  This  crystalization  occasions  brittleness.  The 
greater  the  amount  of  foreign  matter  which  is  combined  with  the 
iron,  the  greater  the  brittleness.  Blows  of  the  hammer  quickly 
repeated,  and  the  exposure  of  the  metal  a  short  time  to  a  low  heat, 
appear  to  be  the  means  of  preventing  crystalization,  at  least,  of 
diminishing  its  extent.  A  sudden  change  of  temperature  augments 
the  power  of  crystalization  in  the  highest  degree.  This  makes  the 
iron  hard,  by  giving  rise  to  so  strong  an  affinity  between  the  iron 
and  foreign  matter,  that  the  color  occasioned  by  the  carbon  dis- 
appears. The  carbon  is  inclosed  in  the  particles  of  iron,  which  is, 
in  turn,  crystalized  by  means  of  its  strongly  cohesive  properties. 
White  plate  metal,  of  great  purity,  containing  carbon  in  large 
amount,  is  harder  than  the  hardest  cast  steel;  but  the  strength  of 
its  cohesive  properties,  and  the  larger  size  of  its  crystals,  are  the 
causes  of  its  brittleness.  The  best  steel,  if  melted  at  a  high  heat, 
similar  to  that  of  the  blast  furnace,  would  appear  in  the  same  form 
as  plate  metal,  and  would  be  quite  as  brittle.  From  the  facts  we 
have  stated,  we  may  draw  the  conclusion  that  the  impurities  which 
increase  the  cohesive  power  of  steel  or  iron  may  be  retained,  and 
the  formation  of  crystals  still  be  prevented. 

V.   Oast  Steel 

The  irregularity  exhibited  in  the  texture  of  common  steel  gave 
rise  to  the  invention  of  cast  steel.  Common  steel  is  broken  into 
small  pieces,  and  closely  packed  into  a  crucible  made  of  good  fire- 
clay. That  which  is,  in  some  degree,  more  highly  carbonized  than 


476 


MANUFACTURE   OF   STEEL. 


usual,  is  best  adapted  for  cast  steel ;  because,  in  the  melting  opera- 
tion, it  loses  a  portion  of  carbon.  Clay  suitable  for  the  manu- 
facture of  crucibles  exists  in  abundance.  Both  slopes  of  the  Alle- 
ghany  Mountains  furnish  fire-clay  whose  quality  is  unsurpassed. 
With  this  clay,  plumbago  or  coke  dust  is  mixed ;  but  neither  of 
these  increases  its  durability,  though  diminishing  its  liability  to 
break  on  account  of  sudden  changes  of  heat.  This  well-mixed  mass 
— to  which  more  attention  should  be  paid  than  that  required  in  the 
manufacture  of  fire  brick — is  firmly  pounded  in  an  iron  mould,  with 
a  movable  cone  for  the  interior.  The  crucible  which  is  thus  formed 
is  air-dried,  and  slightly  burned  before  it  is  employed  in  the  melt- 
ing of  cast  steel.  For  this  purpose,  a  crucible  five  inches  wide  at 
the  top,  and  sixteen  or  eighteen  inches  in  height,  is  generally  em- 
ployed. We  must  take  every  precaution  to  prevent  it  from  crack- 
ing, for  in  such  a  case  its  contents  are  generally  lost. 

P 

Fig.  149. 


Cast  steel  air  furnace. 


Fig.  149  represents  an  air  furnace,  the  construction  of  which  is 
similar  to  those  used  by  brass  founders.     It  is  two  feet  deep,  and 


MANUFACTURE    OF   STEEL.  477 

twelve  inches  square.  The  flue  at  the  top  is  covered  by  a  cast  iron 
trap-door.  The  top  of  the  furnace  coincides  with  the  plane  of  the 
floor  of  the  laboratory.  Under  the  floor  of  the  latter  is  an  arch,  into 
which  the  grates  of  the  furnace  may  be  emptied.  This  arch  sup- 
plies the  fires  with  air,  and  in  it  the  ashes  accumulate.  The  cruci- 
ble is  placed  on  a  support  composed  of  two  thicknesses  of  fire  brick, 
and  its  top  is  covered  with  a  lid.  In  many  cases,  pounded  glass 
and  blast  furnace  cinder  are  laid  on  the  top  of  the  steel,  as  well  to 
prevent  the  access  of  air  as  the  oxidation  of  the  carbon.  But  if  the 
lid  fits  well,  this  precaution  is  unnecessary ;  besides,  these  materials 
generally  tend  to  glaze,  and  as  a  consequence  to  crack,  the  cruci- 
ble. In  large  factories,  ten  or  twenty  furnaces  may  be  put  in  one 
row,  each  furnace  having  its  own  chimney.  In  England,  the  fuel 
employed  is  coke ;  but  our  Pennsylvania  anthracite  is  far  superior 
to  coke  for  this  purpose.  The  more  compact  the  fuel,  the  better 
will  be  the  result.  In  feeding  the  furnace  with,  coal,  we  must  ob- 
serve great  caution,  for  a  sudden  charge  of  cold  fuel  is  apt  to  crack 
the  crucible.  For  this  reason,  square  are  preferable  to  round  fur- 
naces. The  heat  of  the  furnace  must  be  conducted  in  such  a  man- 
ner that  the  melting  shall  commence  from  below,  and  not  from  the 
top.  This  is  another  reason  why  the  form  just  described  is  prefer- 
able to  any  other  form.  All  these  advantages  are  increased  by  the 
employment  of  blast,  which,  of  course,  is  essential  where  anthra- 
cite is  used. 

The  time  required  to  melt  steel  depends  partly  upon  the  draught 
of  the  furnace,  partly  upon  the  quality  of  the  crude  steel,  and  partly 
upon  the  quality  of  the  article  we  design  to  manufacture.  From 
one  to  three  hours  is  generally  required  for  a  crucible  containing 
fifty  pounds  of  metal.  The  stronger  the  steel,  the  greater  the  length 
of  time  consumed.  The  mass  must  become  perfectly  liquid,  no 
matter  how  long  a  time  is  required  to  produce  this  result.  The 
liquid  steel  is  then  poured  into  previously  heated  cast  iron  moulds, 
and  cast  in  the  shape  of  square  or  octagonal  bars,  two  inches  thick. 
Before  casting,  the  steel  in  the  crucible  is  stirred  with  a  hot  iron 
rod,  after  which  a  strong  heat  is  applied  for  a  few  minutes.  After 
casting,  the  top  of  the  steel  in  the  mould  is  covered  with  clay,  to 
prevent  its  blistering,  and  to  prevent  the  access  of  air. 

The  cast  rods  are  exposed  to  a  cherry-red  heat,  and  put,  when 
almost  black,  to  the  hammer.  The  rapid  succession  of  strokes 
heats  the  steel,  and,  if  it  is  very  hard,  often  in  too  high  a  degree. 
Each  hammer  requires  a  tilter,  and  two  boys.  In  this  case,  as  in 


478  MANUFACTURE   OF  STEEL. 

that  of  blistered  or  German  steel,  hammering  and  heating  need  the 
utmost  attention.  The  quality  of  the  steel  depends  upon  the  quick- 
ness with  which  the  work  is  performed.  The  rods  are  heated  in 
heating  stoves  constructed  like  sheet  iron  ovens. 

VI.  Creneral  Remarks. 

It  is  unnecessary  to  enter  upon  a  scientific  investigation  of  the 
principles  involved  in  the  manufacture  of  steel ;  still,  a  few  remarks, 
deduced  from  our  reflections  upon  this  subject,  will,  probably,  not 
be  received  without  interest. 

The  most  remarkable  quality  of  steel  is  its  behavior  in  different 
temperatures.  Nearly  every  kind  of  steel  requires  a  particular 
degree  of  heat  to  impart  to  it  the  greatest  hardness  of  which  it  is 
susceptible.  If  heated,  and  suddenly  cooled  below  that  degree,  it 
becomes  as  soft  as  iron;  if  heated  beyond  that  degree,  it  becomes 
very  hard,  though  brittle;  and  its  brittleness  is  an  indication  of  the 
degree  of  its  heat,  when  cooled  off.  These  are  the  reasons  why,  in 
hardening  steel,  we  generally  overheat,  and  then  temper  it.  To 
hit  the  exact  heat  required  -is,  as  we  have  stated,  a  matter  of  ex- 
treme delicacy.  Steel,  however,  loses  carbon  when  overheated; 
therefore,  in  hardening  it,  no  amount  of  attention  is  superfluous, 
if  we  wish  to  preserve  its  quality.  The  higher  the  heat  at  which 
it  was  manufactured,  the  greater  the  degree  of  heat  it  will  bear  in 
hardening  and  welding.  For  this  reason,  cast  steel  will  not  bear 
so  high  a  heat  as  other  steel.  German  steel  is  produced  by  a 
higher  heat  than  blistered  steel,  and  the  latter  by  a  higher  heat  than 
cast  steel.  Where  large  pieces  are  to  be  welded,  the  German  steel 
is  preferable ;  but  where  welding  in  small  pieces  can  be  accom- 
plished with  the  assistance  of  borax,  cast  steel  will  make  the  better 
article.  Hardness  and  tenacity  depend  entirely  on  the  quality  of 
the  iron  from  which  the  steel  is  made.  The  best  and  strongest 
iron,  smelted  from  the  ore  by  hot  blast,  coke,  or  anthracite,  is  not 
adapted  to  make  good  steel.  Steel  made  from  such  iron  may  serve 
for  springs,  which  do  not  require  a  fine,  close-grained  material;  but 
it  is  not  suitable  for  cutlery  and  tools.  In  addition  to  iron  and 
carbon,  steel  always  contains  impurities.  These  may  be  considered 
an  integral  part  of  its  nature.  But  it  would  be  a  mistake  to  leave 
silicon  in  the  iron,  or  to  introduce  it  purposely,  because  the  best 
steel  contains  silicon.  The  purest  iron  contains  as  much  foreign 
matter  as  the  best  steel  requires. 

The  characteristic  difference  between  iron  and  steel  is  commonly 


MANUFACTURE   OF  STEEL.  479 

explained  by  the  assertion  that  all  iron  which  hardens  by  being 
suddenly  cooled,  is  steel.  This  distinction  we  do  not  recognize  as 
a  correct  one,  because  all  inferior  qualities  of  bar  iron,  and  all  cast 
iron,  will  become  harder  when  chilled.  From  this  rule  the  purest, 
softest,  and  most  fibrous  wrought  iron  is  alone  an  exception.  In 
making  this  assertion,  we  assume,  of  course,  that  the  iron  must  be 
heated,  before  hardening,  to  a  degree  beyond  that  at  which  it  was 
manufactured — just  what,  in  fact,  must  be  done  with  steel  before  it 
is  cooled  in  cold  water — for,  if  heated  at  too  low  a  temperature  and 
then  chilled,  it  will  not  acquire  the  hardness  assumed.  Wrought  or 
cast  iron  generally  becomes  very  brittle,  if  treated  like  steel,  in  con- 
sequence of  the  large  amount  of  foreign  matter  it  contains.  A 
good  test  of  the  quality  of  iron,  designed  for  conversion  into  steel, 
is  its  power  of  retaining  softness,  fibres,  and  tenacity,  after  it  has 
been  hardened.  The  more  hard  and  brittle  it  becomes  after 
hardening,  the  less  adaptation  it  has  for  making  blistered  or  cast 
steel.  There  is  no  decisive  distinction  between  wrought  or  cast 
iron  and  steel,  so  far  as  chemical  composition  is  concerned.  One 
blends  So  gradually  with  the  other,  that  no  point  of  separation  or 
union  is  exhibited  with  sufficient  prominence  to  furnish  a  basis 
upon  which  a  clear,  specific,  chemical  difference  can  be  postulated. 
A  given  kind  of  steel  may  be  far  less  pure  than  some  kinds  of  cast 
iron,  and  this  is  sufficient  proof  that  no  classification,  on  the  ground 
of  chemical  purity  or  impurity,  is  possible  ;  because  we  can  convert 
steel  into  gray  cast  iron  by  tempering,  and  into  white  cast  iron  by 
hardening.  Neither  operation  is  anything  else  than  the  conversion 
of  steel  into  a  given  kind  of  cast  iron  of  greater  or  less  purity. 
Hardened  and  tempered  steel  is  a  medium  between  gray  and  white 
cast  iron.  It  receives  a  portion  of  the  strength  of  the  gray,  and  a 
portion  of  the  hardness  of  the  white,  metal.  It  is  thus  evident  that 
no  distinct  line  can  be  drawn  between  iron  and  steel.  Neverthe- 
less, but  little  experience  is  required  to  enable  the  worker  in  iron 
and  steel  to  distinguish  one  from  the  other.  Steel  is  superior  in 
compactness  to  cast  and  wrought  iron,  for  it  is  harder  under  the 
hammer.  If  heated  beyond  a  certain  temperature,  it  becomes  brit- 
tle, and  cannot  be  wrought  at  all.  The  same  description  applies 
to  some  inferior  wrought  iron,  and  generally  to  cast  iron.  Un- 
der the  hammer,  as  well  as  in  grinding,  steel  assumes  a  brighter 
polish  than  iron.  Steel  has  a  more  uniform,  silvery  sound  than 
iron.  Iron  of  excellent  quality  sounds  very  dull,  like  lead.  The 
most  reliable  criterion  of  steel  is  the  absence  of  all  fibres  and  crys- 


480  MANUFACTURE    OF    STEEL. 

tals.  If  the  fracture  of  a  bar  of  steel  appears  crystaline,  the  steel 
may  be  considered  imperfect — as,  in  fact,  a  kind  of  strong,  cold- 
short iron.  It  will  harden,  of  course,  but  it  will  not  retain  a  sound 
edge,  certainly  not  a  point,  and  it  is  brittle,  like  excellent  cast  iron. 
In  good  steel,  we  are  not  able  to  detect,  by  means  of  the  strongest 
lens  or  microscope,  any  indications  of  a  geometrical  form  of  the 
grain.  The  grains  of  the  fracture  may  be  large,  and  the  fracture 
itself  may  appear  like  that  of  bright  gray  cast  iron.  But  this  is  a 
matter  of  little  consequence,  for  the  size  of  the  grain  can  be  reduced 
by  refining,  even  in  the  blacksmith's  fire,  and  by  hammering.  By 
melting  it  in  a  crucible,  we  can  make  cast  steel  of  it.  But  the 
grains  of  steel  must  be  round,  however  small  or  large  they  may  be. 
This,  of  course,  applies  to  steel  which  is  not  too  much  hardened.  If 
too  much  heated  and  hardened,  the  best  steel  will  be  crystaline  in 
its  fracture. 

Several  years  ago,  various  experiments  were  made  by  English, 
French,  and  German  scientific  men,  to  make  steel  by  artificial 
alloys,  that  is,  by  combining  iron  with  other  metals.  Experiments 
were  also  made  to  impregnate  iron  with  carbon  by  a  different 
method  than  that  usually  employed,  namely,  by  means  of  cement 
in  the  chest.  But  none  of  these  experiments  resulted  in  any  prac- 
tical advantage.  Time,  and  iron  of  good  quality,  are  indispensa- 
ble conditions  of  success  in  the  manufacture  of  steel.  Slight  altera- 
tions in  the  cement  may  prove  advantageous;  but  there  is  no  rational 
probability  that  we  shall  ever  succeed  in  manufacturing  good  steel 
from  bad  iron.  As  we  have  stated  once  before,  pure  iron  is  per- 
fectly useless  for  any  other  practical  purpose.  Steel  is  made  of  iron 
which,  generally  speaking,  contains  a  smaller  amount  of  impurities 
than  other  iron.  Still,  there  may  be  bar  iron  which  contains  less 
foreign  matter  than  steel ;  but  it  is  the  form  in  which  foreign 
matter  is  present  which  distinguishes  the  one  from  the  other.  A 
theoretical  investigation  of  this  subject,  however  interesting,  would 
lead  us  too  far  beyond  our  limits.  Nevertheless,  we  shall  observe 
that  white  plate  iron,  of  the  best  quality,  containing  generally  from 
three  to  four  per  cent,  of  carbon,  is  the  hardest  kind  of  iron,  harder 
even  than  the  best  cast  steel.  Still,  it  is  brittle,  and  is  not  sus- 
ceptible of  being  drawn  out  by  the  hammer.  Steel  contains  all  the 
impurities  of  the  iron  from  which  it  is  made,  while  the  iron  gene- 
rally contains  the  impurities  existing  in  the  ore  from  which  it  was 
made,  and  in  the  coal  and  fluxes  employed  in  smelting  it.  Steel 
contains  carbon,  sulphur,  phosphorus,  silicon,  arsenic,  antimony, 


MANUFACTURE   OF   STEEL. 


481 


copper,  tin,  and  manganium ;  and  the  best  English  cast  steel  con- 
tains nitrogen.  The  latter,  of  course,  cannot  be  present  in  any 
other  form  than  in  combination  with  carbon,  thus  forming  a  cyanide 
of  iron.  Among  these  impurities,  carbon  and  silicon  hold  the  first 
rank ;  then  follow  sulphur,  arsenic,  and  manganium.  The  elas- 
ticity and  strength  of  the  Solingen  steel  result  from  the  presence 
of  nearly  0.4  per  cent,  of  copper ;  and  the  excessive  hardness  of 
some  French  steel  results  from  the  presence  of  manganium.  The 
hardest,  though  not  the  strongest,  kind  of  steel  is  the  finer  quality 
of  Styrian  steel.  This  is  pure  iron,  containing  1.13  per  cent,  of 
carbon.  In  order  better  to  elucidate  this  subject,  we  shall  insert 
the  following  table,  exhibiting  the  various  compositions  of  steel : — 


COMPOSITION  OF  STEEL. 

1 

2 

3 

4 

5 

6 

Iron     - 

98.06 

97.94 

93.80 

97.88 

98.87 

98.44 

Carbon         - 

1.94 

1.72 

1.43 

1.70 

1.13 

0.97 

Sulphur       - 

trace 

1.00 

trace 

trace 

trace 

Phosphorus          - 

Silicon          -.-'•- 

trace 

0.22 

0.52 

0.04 

trace 

0.50 

Arsenic        -        ... 

0.07 

0.93 

Antimony    -        -        -        - 

0.12 

Nitrogen      - 

0.18 

Copper 

trace 

0.07 

0.38 

Tin      

trace 

trace 

Manganium         - 

0.02 

1.92 

No.  1  is  Styrian  steel,  celebrated  for  hardness  and  elasticity.  It 
is  called  Brescia  steel,  and  is  principally  sold  in  Italy,  where  quality 
is  made  an  object  of  special  attention  by  the  cutler  and  blacksmith. 
No  2,  common  English  cast  steel,  and  No.  3,  the  best  razor  steel 
from  Sheffield.  No.  4,  Solingen,  or  Siegen  steel,  known  to  be 
very  tough.  No.  5,  very  hard  Styrian  steel.  No.  6,  inferior 
Styrian  steel.  A  critical  examination  of  this  table  will  enable  us 
to  see  clearly  what  is  necessary  to  constitute  good  steel.  The  steel 
which  contains  most  impurities  is  No.  3.  It  is  generally  uniform 
and  hard,  but  very  fusible ;  it  cannot  bear  heat.  No.  5  may  be 
considered  harder  than  No.  3;  but  it  is  brittle,  and  will  not  re- 
ceive a  fine  edge.  No.  1  is  less  hard  than  No.  5,  but  it  is  better 
adapted  for  cutlery  and  weapons.  No.  4  is,  of  all  others,  most 
suitable  for  swords ;  indeed,  for  this  purpose,  it  is  very  little  infe- 
rior to  Damascus  steel.  It  is  not  so  well  adapted  as  No.  3  for 
cutlery,  nor  equal  to  No.  5  for  mint  stamps. 

We  misapply  words  when  we  appropriate  the  term  impurities  to 
31 


482  MANUFACTURE   OF  STEEL. 

the  matter  which,  independently  of  iron,  steel  contains.  These  im- 
purities are  essential  elements  in  its  constitution ;  and,  it  appears, 
the  greater  the  variety,  the  better  the  steel.  In  what  way  these 
admixtures  are  brought  into  the  iron,  we  are  unable  to  say ;  but  a 
careful  examination  of  the  ores  from  which  the  iron  is  made  will 
enable  us  faintly  to  approximate  towards  the  solution  of  this  ques- 
tion. The  ore  from  which  No.  1  was  derived  is  a  very  pure  car- 
bonate of  iron  and  manganese.  No.  2  was  derived  from  common 
Swedish  or  Russian  iron,  both  of  which  were  smelted  from  magnetic 
ore.  This  ore  frequently  contains  sulphur,  silex,  titanic  acid,  and 
copper.  No.  3  was  made  from  Danemora  iron,  the  latter  smelted 
from  magnetic  ore.  The  Danemora  ore  contains,  in  addition  to 
iron,  a  variety  of  matter.  We  may  thus,  in  some  measure,  account 
for  the  presence  of  so  large  an  amount  of  foreign  matter  in  the 
steel.  The  ore  whence  No.  4  was  obtained  contains  a  large  amount 
of  manganese,  always  a  little  copper,  sulphur,  silex,  and  often  a 
small  amount  of  spar  of  lime  and  clay.  It  is  a  crystallized  car- 
bonate, or  spathic  ore.  Nos.  5  and  6,  like  No.  1,  were  obtained 
from  a  very  pure  carbonate  of  iron  and  manganese.  Some  of  the 
admixtures  may  enter  into  combination  with  the  iron  in  the  cement 
box;  but  this  is  not  the  case  with  others.  Carbon,  sulphur,  phos- 
phorus, nitrogen,  and  probably  arsenic,  may  be  united  with  the 
rods  during  the  process  of  cementation ;  but  silicon,  antimony,  cop- 
per, tin,  and  manganium  are  present  in  the  iron  before  it  is  exposed 
to  this  operation.  These  investigations  show  more  clearly  than  any 
we  have  yet  presented,  the  advantages  resulting  from  mixing  ores, 
if  a  given  variety  of  admixtures  is  not  already  contained  in  the  ore. 
Where  wrought  and  cast  iron  are  strong  and  fine,  and  contain, 
besides  a  variety  of  matter,  carbon  and  silicon,  the  steel  which  is 
made  from  them  will  be  of  the  same  character.  It  has  been  pro- 
posed to  manufacture  steel  by  melting  cast  iron  along  with  those 
materials  which  would  purify  it,  and  still  leave  carbon — such  as 
alkaline  matter,  wrought  iron,  and  iron  ore ;  or  by  melting  wrought 
iron  or  pure  oxide  of  iron  along  with  carbon,  in  a  crucible.  No 
such  experiments  amount  to  anything.  Though  they  should  be 
successful,  their  expensiveness  is  so  great  that  they  will  never  be 
productive  of  any  practical  result. 

The  hardening  of  steel  may  be  perfectly  understood  by  studying 
its  nature.  In  endeavoring  to  arrive  at  the  temperature  best  adapted 
to  a  particular  case — a  case,  for  instance,  in  which  we  have  to  deal 
with  a  strange  kind  of  steel — a  practical  test,  namely,  drawing  the 


MANUFACTURE   OF  STEEL.  483 

bar  into  a  tapered  point,  or  chisel,  is  applied.  This  wedge-shaped 
chisel  will,  of  course,  be  more  warm  towards  the  point  than  at  the 
thick  part ;  and  it  is  evident  that  this  part  will,  when  cooled  in  the 
same  cold  medium,  be  harder  than  the  thick  part.  By  breaking, 
and  continuing  to  break  off  the  point,  the  difference  of  grain  will 
show  the  different  temperatures  which  have  been  applied.  The 
finest  and  closest  grain  is  considere  d  the  best.  In  hardening  such 
steel,  it  is  heated  with  due  relation  to  the  degree  of  the  test  heat. 
Though  this  manipulation  is  very  imperfect,  careful  and  intelligent 
workmen  are  generally  quite  successful  in  arriving  at  a  knowledge 
of  what  degree  is  favorable.  The  degree  of  hardness  depends,  in 
some  measure,  upon  the  heat  of  the  steel,  but  mainly  upon  the 
difference  between  the  heat  of  the  steel  and  that  of  the  water  or 
medium  in  which  it  is  cooled.  The  coldest  water  will  make  the 
hardest  steel.  Mercury  is  better  adapted  to  harden  steel  than 
water;  so  is  water,  acidulated  with  any  kind  of  acid,  or  contain- 
ing any  kind  of  salt  in  solution. 

The  process  of  hardening  is  performed  with  due  relation  to  the 
quality  of  the  steel  and  the  purposes  for  which  it  is  designed.  In 
most  instances,  the  hardening  is  effected  in  water,  or  brine.  Saw 
blades  are  thus  hardened,  after  being  heated  in  melted  lead.  Sabres 
are  heated  in  a  suffocated  fire  of  charcoal,  and  then  swung  rapidly 
through  the  air.  Mint  stamps  are  hardened  in  oil,  or  metallic  com- 
positions. The  common  method  of  procedure  in  hardening  is  this : 
The  steel  is  overheated,  cooled  in  cold  water,  and  then  annealed  or 
tempered  by  being  so  far  re-heated  that  oil  and  tallow  will  burn  on 
its  surface ;  or  the  surface  is  ground  and  polished,  and  the  steel 
re-heated  until  it  assumes  a  certain  color.  The  gradations  of  color 
consecutively  follow :  a  light  straw  yellow,  violet,  blue,  and  finally 
gray  or  black,  when  the  steel  again  becomes  as  soft  as  though  it 
had  never  been  hardened. 


CONCLUSION. 


IT  is  evident  that  the  quality  and  quantity  of  iron  we  are  enabled 
to  produce  depend,  in  a  great  measure,  upon  the  nature  and  quali- 
ties of  the  ore  at  our  disposal.  By  means  of  science  and  industry, 
great  difficulties  can  be  overcome.  But  the  only  condition  upon 
which  we  can  rationally  base  any  hope  for  the  future  relative 
to  iron  manufacture  and  its  collateral  branches,  consists  in  the 
union  of  natural  advantages  with  skill,  activity,  and  intellectual 
cultivation.  The  conditions  which  favor  the  manufacture  of  iron, 
in  this  country,  are  so  superior  to  those  which  exist  in  Europe, 
that  any  comparison  between  them  would  be  useless,  if  not  inad- 
missible. Our  immense  ore  deposits  are  unparalleled  in  the  known 
world.  Our  hills  are  covered  with  a  rich  growth  of  timber  ;  and 
the  bowels  of  the  earth  abound  in  stone  coal  of  the  most  advan- 
tageous quality.  True,  we  are  excluded  from  foreign  markets  by 
the  high  price  which  labor  commands;  but  this  obstacle  will,  in 
time,  we  have  no  doubt,  be  effectually  removed  by  the  energy  and 
perseverance  of  our  countrymen.  The  application  of  science  and 
machinery,  in  the  manufacture  of  iron,  does  not  exhibit  so  high  a 
state  of  cultivation  as  we  find  in  other  departments  of  labor,  such 
as  the  manufacture  of  calico  prints  and  silks ;  but,  when  the  prin- 
ciples involved  in  this  interesting  and  highly  important  branch  of 
industry  are  once  thoroughly  understood  by  our  artisans,  results 
will  show  that  the  low  price  of  labor  will  prove  of  no  advantage 
over  a  skillful  and  inventive  intellect. 

This  branch  of  industry  presents  a  wide  field  for  the  exhibition 
of  skill  and  enterprise.  After  an  advantageous  location  for  an 
establishment  is  selected,  the  fundamental  object  which  the  intel- 
ligent manufacturer  should  seek  to  secure  is  the  improvement  of 
the  quality  of  iron.  We  repeat,  to  this  object  every  other  should 
be  regarded  as  subordinate.  He  who  best  understands  what  is 
necessary  to  improve  its  quality,  is  most  competent  to  work  cheaply. 
We  have  an  abundance  of  inferior  iron  already  in  the  market; 


CONCLUSION.  485 

therefore,  but  little  advantage  would  result  from  an  attempt  to 
produce  it  more  cheaply  than  it  is  at  present  furnished.  In  fact, 
so  limited  are  its  uses,  that  such  an  attempt  would  tend  to  reduce 
its  price  even  below  its  relative  value.  Inventors  should  know 
what  is  the  legitimate  range  of  improvement.  It  is  vain  to  think 
of  excelling  the  speed  of  the  magnetic  telegraph. 

A  thorough  knowledge  of  the  nature  of  iron,  fuel,  and  ore  is 
essential  to  the  manufacturer  who  aims  to  realize  all  the  advan- 
tages his  business  can  afford  him  Qualitative  improvements  are,  in 
fact,  based  upon  a  knowledge  of  the  chemical  composition  of  ore, 
coal,  and  fluxes,  with  their  chemical  relations,  and  upon  a  know- 
ledge of  the  composition  of  cinders,  and  the  laws  which  govern 
their  formation.  A  diligent  study  of  the  nature  of  iron  in  its  various 
forms,  and  in  its  relations  to  other  matter,  will  not  only  enable  the 
manufacturer  to  obtain  the  most  valuable  articles  from  given  mate- 
rials, but  it  will  enable  him  to  modify  his  product  in  accordance 
with  the  state  of  the  market,  and  the  wants  of  the  times.  This 
knowledge  alone  will  liberate  him  from  the  incumbrances  occa- 
sioned by  unfavorable  materials  and  the  high  price  of  labor.  Per- 
haps in  no  manufacture  is  rational  and  skillful  management  so 
indispensable  an  element  of  success  as  in  that  of  iron.  Hence, 
the  difference  in  success  between  different  individuals,  where  locality 
and  materials  have  been  equally  favorable.  Neither  education  nor 
superior  means  is  a  guarantee  of  prosperity.  A  vigorous  applica- 
tion of  the  reasoning  faculties  alone  will  secure  victory  in  a  close 
contest  of  competition. 


APPENDIX. 


TABLE  I. 

Composition  of  Crude  Cast  Iron,  from  German  Iron  Works. 


1 

2 

3 

4 

5 

6 

Iron     

93.66 

91.98 

91.42 

93.29 

86.73 

95.81 

Free  carbon.     Plumbago    - 

3.85 

3.48 

2.71 

1.99 

2.38 

3.04 

Latent  carbon.     Chem.  comb. 

0.48 

0.95 

1.44 

2.78 

2.08 

0.57 

Sulphur       - 

trace 

trace 

trace 

trace 

trace 

trace 

Phosphorus          - 

1.22 

1.68 

1.22 

1.23 

0.08 

Silicon         .... 

0.79 

1.91 

3.21 

0.71 

1.31 

0.57 

Aluminum  - 

trace 

trace 

trace 

trace 

Manganese  - 

trace 

trace 

trace 

trace 

7.42 

No.  1.  German  pig  iron  of  good  quality,  from  brown  hematite 
ore,  pine  charcoal,  and  cold  blast;  it  is  gray  and  strong.  No.  2. 
Grayer  than  No.  1 ;  from  the  same  ore,  coal,  and  furnace,  but 
smelted  by  blast  of  195°.  No.  3.  Gray  pig  iron,  smelted  from 
hematite  ore  by  hard  charcoal,  and  blast  of  400°.  No.  4.  Mottled 
iron,  from  the  same  ore,  coal,  and  furnace;  but  smelted  by  cold 
blast.  A  remarkable  difference  may  be  observed  between  these 
specimens  with  respect  to  the  amount  of  silicon  they  contain.  No. 
5.  Gray  iron,  smelted  from  three  parts  of  spathic,  and  two  parts 
of  brown  hematite  ore;  it  is  very  hard  and  strong.  No.  6.  Gray 
coke  iron,  from  Koenigshuette,  Silesia. 


APPENDIX. 


48T 


TABLE  II. 

Composition  of  Gray  Pig  Iron. 


1 

2 

3 

4 

5 

6 

Iron     - 

90.57 

92.87 

94.63 

92.30 

92.24 

93.39 

Free  carbon.     Plumbago     - 
Latent  carbon.    Chem.  comb. 

I  3.38 

2.34 
0.93 

1.40 
1.20 

1.80 
0.40 

1.52 

0.30 

0.18 
1.00 

Sulphur       -        ... 

0.18 

0.06 

0.35 

1.40 

0.60 

3.75 

Phosphorus          -        -        - 

0.75 

0.39 

1.30 

0.95 

0.38 

Silicon     ..... 

4.86 

3.37 

1.53 

2.80 

1.79 

1.30 

Aluminum  -        -        -        - 

1.01 

Copper         -        -        -        - 

0.10 

Manganese  -        -        -        - 

1.23 

0.50 

2.60 

No.  1.  Gray  pig  iron  of  France.  No.  2.  Gray  iron  of  Germany, 
smelted  from  a  mixture  of  red  clay  ore,  compact  carbonate,  and 
brown  hematite;  it  is  a  strong  iron.  No.  3.  Gray  Scottish  coke 
iron,  from  the  Calder  Iron  Works.  No.  4.  Gray  coke  iron,  from 
Scotland,  Clyde  Iron  Works.  No.  5.  White  plate  metal,  from  the 
same  works.  No.  6.  French  white  pig  iron,  from  Finny;  very 
short  and  brittle. 


TABLE  III. 

Composition  of  White  Crude  Pig  Iron,  Steel  Metal. 


1 

2 

3 

4 

5 

6 

T 

86  66 

88  96 

89  71 

89  80 

9406 

89  63 

Latent  carbon.    Chem.  comb. 

5.80 

5.44 

5.14 

5.41 

4.26 

3.82 

Sulphur       - 

0.65 

trace 

0.05 

Phosphorus 
Silicon         -        -        -        - 

1.86 

0.18 

0.08 
0.56 

trace 
0.37 

0.08 

0.05 
0.17 

Aluminum  - 

0.11 

Arsenic        -        -        -        - 

4.05 

Nitrogen      -        -        -        - 
Copper         -        - 
Manganese  -        - 

0.87 

1.20 
0.17 
4.00 

4.50 

0.18 
4.24 

0.75 
0.85 

0.08 
6.95 

All  -the  specimens  included  in  this  table,  with  the  exception  of 
No.  1,  which  is  of  French  origin,  are  German;  and  all  are  speci- 
mens of  white  plate  iron,  smelted  from  rich  spathic  iron  ore. 


488 


APPENDIX. 


TABLE  IV. 

Composition  of  White  Crude  Pig  Iron,  from  Heavy  Burden. 


1 

2 

3 

4 

5 

6 

Iron     

95.14 

92.26 

95.20 

91.26 

95.19 

91.90 

Latent  carbon      -        -        - 

3.18 

3.02 

2.91 

2.75 

1.91 

1.40 

Sulphur       .... 

trace 

0.01 

0.38 

1.11 

0.30 

Phosphorus          - 

0.40 

0.08 

2.30 

Silicon         -        ... 

0.53 

0.33 

trace 

0.48 

1.01 

4.10 

Aluminum  -        -        -        - 

0.01 

0.06 

Arsenic       .... 

4.08 

Nitrogen      - 

0.93 

1.04 

0.72 

Copper         -        -        -        - 

0.11 

Manganese          - 

0.22 

3.27 

1.79 

Nos.  1  and  2.  Smelted  by  charcoal  from  a  mixture  of  spathic 
ore  and  forge  cinders;  No.  3,  from  spathic  ore  and  heavy  burden. 
Nos.  4,  5,  and  6.  Specimens  of  French  pig  metal,  from  Alais, 
Creuzot,  and  Firmy;  the  latter  is  very  brittle.  The  first  three 
are  German  specimens,  of  a  strong,  excellent  quality. 


TABLE  V. 

Composition  of  Wrought  Iron. 


1 

2 

3 

4 

5 

6 

Iron     -        -        -        - 

98.78 

99.13 

98.90 

98.88 

99.73 

99.87 

Carbon        - 

0.84 

0.66 

0.41 

0.40 

0.24 

0.09 

Sulphur       - 

trace 

trace 

Phosphorus          ... 

0.40 

trace 

Silicon         - 

0.12 

trace 

0.08 

0.01 

0.03 

0.03 

Arsenic        - 

0.02 

Copper 

0.07 

0.05 

0.32 

Manganese          ... 

0.05 

0.29 

0.04 

0.30 

trace 

No.  1.  Swedish  iron,  from  Danemora.  No.  2.  Very  strong  Ger- 
man rod  iron.  No.  3.  English  puddled  iron,  from  Wales.  No.  4. 
Compact,  strong  German  iron,  from  the  Hartz  Mountains.  No.  5. 
Common  Swedish  bar  iron.  No.  6.  Fibrous,  but  weak  German 
iron. 


APPENDIX. 


489 


TABLE  VI. 


AnagrapTi,  exhibiting  the  Decomposition  and  decomposition  of  Materials 
the  Blast  Furnace. 


in 


fcn 


MATERIALS. 

I*  Oxygen    -    .     - 
j  Nitrogen  -    .    .     . 

•I  Steam    J  °x^en 
£  hydrogen 

Carbonic  acid  J 


r 


Iron    -    -    - 
Oxygen    -    - 

Carbonic  acid 


carbon  - 


\  oxygen  - 
(  carbon  - 

Silex  J  oxYsen  -    -     -     - 
( silicon    -     -     -     - 

Alumina   \  °^en     - 

(  aluminum     • 

Manganese  <  Oxy8en 

{  manganium 
T  imo     5  oxygen    -     -     - 

JLrflUio         <  , 

I  calcium  -  -  - 
Phosphorus  -  -  -  .  . 
Sulphur,  &c.  -  .  .  . 

Carbon 

Hydrogen     .     .     .     .     . 
Nitrogen  ----_. 

Oxygen    

Potash      -     -    - 


Silex  %    ... 

{  silicon   - 

,  Sulphur,  &c.      ... 

Lime     }«2f*    '    - 
I  calcium  -    . 

Carbonic  acid    5  carbon 
£  oxygen 
o:j-_  5  oxygen  -    -    - 

cllcX  \     .,. 

(  silicon    ... 

A i  •  ^  oxvsen 
Alumina  <  */s^" 
,  f  aluminum 


PRODUCTS. 

(At  the  trunnel  head : 
Carbonic  acid;  carbo- 
nic oxide;  steam;  hy- 
drogen; nitrogen;  va- 
pors of  metals;  the 
oxides  of  metals,  &c. 


f  In  the  hearth :  Crude 
iron — containing  iron  ; 
J  carbon;  silicon;  man- 

jganium;  phosphorus; 
sulphur ;  nitrogen ;  alu- 

(^  minum ;  calcium,  &c. 


In  the  hearth:  Cin- 
der— a  composition  of 
silicates  and  alumin- 
ates,  carbonates,  phos- 
phates, sulphurets,  and 
phosphurets;  and  of 
lime,  protoxide  of  man- 
ganese, protoxide  of 
iron,  potash,  &c. 


TABLE  VII. 


Specific  Gravity  of  Matter. 


Atmospheric  air 
Nitrogen 
Carbonic  acid 
Carbonic  oxide 
Hydrogen 
Pit  gas 
Light  gas 


1.000 
0.975 
1.524 

0.967 
0.068 
0.558 
0.985 


Water 
Platinum 
Mercury 
Copper 
Iron,  cast 
Iron,  rod 
Steel    - 


-  1.000 

-  19.5 

-  13.5 

-  8.7 

-  7.2 

-  7.7 

-  7.8 


490  APPENDIX. 

TABLE  VIII. 

Degrees  of  Heat  generated  by  Perfect  Combustion. 

Degrees. 

Air-dried  wood,  containing  twenty  per  cent,  of  water        -  2867 

Half  kiln-dried  wood  -  3047 

Very  dry  kiln-dried  wood      -  -  3182 

Green  turf      -  ...  2732 

Best  kind  of  turf,  kiln  dried,  and  free  of  ashes       -  -  3632 

Bituminous  coal         -  -  -  4082 

Anthracite  coal          ------  4170 

Charcoal  of  wood      ------  4352 

Brown  charcoal  of  wood        -  -  3902 

Coke,  with  ten  per  cent,  of  hygroscopic  water        -        -    -  4262 

Coke,  dry       -  -  4352 

Gas  from  the  top  of  a  charcoal  blast  furnace  -  2192 

Gas  tapped  ten  feet  below  the  top  of  a  charcoal  blast  furnace  2912 

Gas  from  a  coke  furnace  on  the  top  -  2192 

"      sixteen  feet  below  the  top  -  3182 


TABLE  IX. 

Degrees  of  Heat  at  which  the  following  Substances  melt. 

Platinum        -  '-  -  -  -  -  4593 

Wrought  iron  -  -  -  -  3632 

Steel   -  -  -  -  -  -  -  3272 

Cast  iron        -  -  2912 

Blast  furnace  cinders  ...  -  2552 

Copper •-  2138 

Gold 2015 


TABLE  X. 


Capacity  of  Matter  for  Latent  Heat. 

Water 1.000 

Steam  --.....        0.847 


Nitrogen 
Carbonic  oxide 
Carbonic  acid 
Oxygen 
Hydrogen 
Atmospheric  air 
Steel 

Crude  iron 
Wrought  iron 


0.275 
0.288 
0.221 
0.236 
3.294 
0.267 
0.118 
0.129 
0.113 


APPENDIX. 


491 


TABLE  XL 

Degrees  of  Expansion  of  Air  ly  Heat,  in  a  given  Bulk. 


320 
1000 


500 

1043 


750 
1099 


1000 

1152 


1500 

1255 


2000 

1364 


2120 

1376 


TABLE  XII. 

Weight  in  Pounds  of  one  Cubic  Foot  of  the  following  Substances. 


Cast  iron    - 

Wrought  iron 

Steel 

Pine  wood 

Water 

Air 

Steam 


450. 
486. 
489. 
29.5 
62.5 
0.075 
0.036 


TABLE  XIII. 

Weight  of  a  Superficial  Foot  of  Plate,  or  Sheet  Iron. 


No.  of  the 
wire  gauge. 

Thickness  in 
inches. 

Weight  in 
pounds. 

No.  of  the 
wire  gauge. 

Thickness  in 
inches. 

Weight  in 
pounds. 

1 

40. 

12 

4.38 

| 

35. 

13 

3.75 

30. 

14 

3.12 

H 

27.5 

15 

2.82 

¥ 

25. 

16 

TV 

2.50 

T9F 

22.5 

17 

2.18 

1 

20. 

18 

1.86 

A 

17.5 

19 

1.70 

I 

15. 

20 

1.54 

1 

& 

12.5 

21 

1.40 

2 

12. 

22 

A 

1.25 

3 

11. 

23 

1.12 

4 

£ 

10. 

24 

1. 

5 

8.74 

25 

0.9 

6 

8.12 

26 

0.8 

7 

A 

7.5 

27 

0.72 

8 

6.86 

28 

A 

0.64 

9 

6.24 

29 

0.56 

10 

5.62 

30 

0.50 

11 

* 

5. 

492 


APPENDIX. 


TABLE  XIV. 

Weight  of  Rod  Iron  one  Foot  in  length,  of  the  following  Dimensions. 


SQUARE  IRON. 

ROUND  IRON. 

FLAT  IRON. 

Inch. 

Pounds. 

Inch. 

Pounds  . 

Inch. 

Pounds. 

i 

0.2 

* 

0.14 

Ixi 

0.8 

| 

0.5 

I 

0.4 

1    1 

1.3 

I 

0.8 

£ 

0.7 

1.7 

f 

1.3 

f 

1. 

f    1 

2.1 

f 

1.9 

I 

1.5 

1    1 

2.5 

2.6 

* 

2. 

i      2 

1.7 

1^ 

3.4 

1 

;2.7 

1      2 

2.5 

H 

4.3 

It 

3.4 

£      2 

3.4 

H 

5.3 

1* 

4.2 

f      2 

4.2 

if 

6.4 

If 

5. 

1      2 

5.1 

1 

7.6 

6. 

i      3 

2.5 

1 

8.9 

If 

7. 

1      3 

3.8 

li 

10.4 

If 

8.1 

£      3 

5.1 

1 

11.9 

If 

9.3 

f      3 

6.3 

2 

13.5 

2 

10.6 

f      3 

7.6 

2J 

17.1 

2J 

13.5 

\      4 

3.4 

2^ 

21.1 

2£ 

16.7 

1      4 

5.1 

2f 

25.6 

2f 

20.1 

*      4 

6.8 

3 

30.4 

3 

23.9 

f      4 

8.4 

3& 

41.4 

3* 

32.5 

f      4 

10.1 

4 

54.1 

4 

42.5 

i      5 

4.2 

5 

84.5 

5 

66.8 

1      5 

6.3 

6 

121.7 

6 

95.6 

8.4 

7 

165.6 

7 

130. 

f      5 

10.6 

8 

216.3 

8 

169.9 

f      5 

12.7    - 

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